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PART C Other Information
TABLE OF CONTENTS
INDEX TO FINANCIAL STATEMENTS

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As filed with the Securities and Exchange Commission on July 31, 2013

Securities Act File No. 333-183555

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Form N-2

REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

Post-Effective Amendment No. 4

Main Street Capital Corporation
(Exact name of registrant as specified in charter)

1300 Post Oak Boulevard, Suite 800
Houston, TX 77056
(713) 350-6000
(Address and telephone number, including area code, of principal executive offices)

Vincent D. Foster
President and Chief Executive Officer
Main Street Capital Corporation
1300 Post Oak Boulevard, Suite 800
Houston, TX 77056
(Name and address of agent for service)

COPIES TO:

Approximate date of proposed public offering:
From time to time after the effective date of this Registration Statement.

        If any securities being registered on this form will be offered on a delayed or continuous basis in reliance on Rule 415 under the Securities Act of 1933, other than securities offered in connection with a dividend reinvestment plan, check the following box. ý

        It is proposed that this filing will become effective (check appropriate box): ý when declared effective pursuant to section 8(c).

   

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The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED JULY 31, 2013

PROSPECTUS

$800,000,000

Main Street Capital Corporation

Common Stock
Preferred Stock
Warrants
Subscription Rights
Debt Securities
Units

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           We may offer, from time to time in one or more offerings, up to $800,000,000 of our common stock, preferred stock, warrants representing rights to purchase shares of our common stock, preferred stock, or debt securities, subscription rights, debt securities or units, which we refer to, collectively, as the "securities." Our securities may be offered at prices and on terms to be disclosed in one or more supplements to this prospectus. The offering price per share of our common stock, less any underwriting commissions or discounts, will not be less than the net asset value per share of our common stock at the time of the offering, except (i) with the requisite approval of our common stockholders or (ii) under such other circumstances as the Securities and Exchange Commission may permit. In this regard, on June 14, 2012, our common stockholders voted to allow us to issue common stock at a price below net asset value per share for the period ending on June 13, 2013, the date of our 2013 Annual Meeting of Stockholders. Our stockholders did not specify a maximum discount below net asset value at which we are able to issue our common stock, although the number of shares sold in each offering may not exceed 25% of our outstanding common stock immediately prior to such sale. In addition, we cannot issue shares of our common stock below net asset value unless our Board of Directors determines that it would be in our and our stockholders' best interests to do so. We are not seeking an extension of the shareholder authorization to issue common stock at a price below net asset value per share at our 2013 Annual Meeting of Stockholders because our common stock price per share has been trading significantly above the current net asset value per share of our common stock, but we may seek such authorization at future Annual Meetings or Special Meetings of Stockholders. Sales of common stock at prices below net asset value per share dilute the interests of existing stockholders, have the effect of reducing our net asset value per share and may reduce our market price per share. In addition, continuous sales of common stock below net asset value may have a negative impact on total returns and could have a negative impact on the market price of our shares of common stock. See "Sales of Common Stock Below Net Asset Value."

           Shares of closed-end investment companies such as us frequently trade at a discount to their net asset value. This risk is separate and distinct from the risk that our net asset value per share may decline. We cannot predict whether our common stock will trade above, at or below net asset value. You should read this prospectus and the applicable prospectus supplement carefully before you invest in our common stock.

           Our securities may be offered directly to one or more purchasers through agents designated from time to time by us, or to or through underwriters or dealers. The prospectus supplement relating to the offering will identify any agents or underwriters involved in the sale of our securities, and will disclose any applicable purchase price, fee, commission or discount arrangement between us and our agents or underwriters or among our underwriters or the basis upon which such amount may be calculated. See "Plan of Distribution." We may not sell any of our securities through agents, underwriters or dealers without delivery of a prospectus supplement describing the method and terms of the offering of such securities, which must be delivered to each purchaser at, or prior to, the earlier of delivery of a confirmation of sale or delivery of the securities.

           We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies and debt capital to middle market ("Middle Market") companies. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million.

           The LMM and Middle Market securities in which we invest generally would be rated below investment grade if they were rated by rating agencies. Below investment grade securities, which are often referred to as "junk," have predominantly speculative characteristics with respect to the issuer's capacity to pay interest and repay principal. They may also be difficult to value and are illiquid.

           Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company.

           We are an internally managed, closed-end, non-diversified management investment company that has elected to be treated as a business development company under the Investment Company Act of 1940.

           Our common stock is listed on the New York Stock Exchange under the symbol "MAIN." On July 30, 2013, the last reported sale price of our common stock on the New York Stock Exchange was $30.80 per share, and the net asset value per share of our common stock on March 31, 2013 (the last date prior to the date of this prospectus on which we determined our net asset value per share) was $18.55.

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           Investing in our securities involves a high degree of risk, and should be considered highly speculative. See "Risk Factors" beginning on page 15 to read about factors you should consider, including the risk of leverage and dilution, before investing in our securities.

           This prospectus and the accompanying prospectus supplement contain important information about us that a prospective investor should know before investing in our securities. Please read this prospectus and the accompanying prospectus supplement before investing and keep them for future reference. We file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission. This information is available free of charge by contacting us at 1300 Post Oak Boulevard, Suite 800, Houston, Texas 77056 or by telephone at (713) 350-6000 or on our website at www.mainstcapital.com. Information contained on our website is not incorporated by reference into this prospectus, and you should not consider that information to be part of this prospectus. The Securities and Exchange Commission also maintains a website at www.sec.gov that contains such information.

           Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

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The date of this prospectus is                    , 2013

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        This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission, or SEC, using the "shelf" registration process. Under the shelf registration process, we may offer, from time to time, up to $800,000,000 of our securities on terms to be determined at the time of the offering. This prospectus provides you with a general description of the securities that we may offer. Each time we use this prospectus to offer securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. To the extent required by law, we will amend or supplement the information contained in this prospectus and any accompanying prospectus supplement to reflect any material changes to such information subsequent to the date of the prospectus and any accompanying prospectus supplement and prior to the completion of any offering pursuant to the prospectus and any accompanying prospectus supplement. Please carefully read this prospectus and any accompanying prospectus supplement together with the additional information described under "Available Information" and "Risk Factors" before you make an investment decision.

        No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus or any accompanying supplement to this prospectus. You must not rely on any unauthorized information or representations not contained in this prospectus or

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any accompanying prospectus supplement as if we had authorized it. This prospectus and any accompanying prospectus supplement do not constitute an offer to sell or a solicitation of any offer to buy any security other than the registered securities to which they relate, nor do they constitute an offer to sell or a solicitation of an offer to buy any securities in any jurisdiction to any person to whom it is unlawful to make such an offer or solicitation in such jurisdiction. The information contained in this prospectus and any accompanying prospectus supplement is accurate as of the dates on their covers.

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RISK FACTORS

        Investing in our securities involves a number of significant risks. In addition to the other information contained in this prospectus and any accompanying prospectus supplement, you should consider carefully the following information before making an investment in our securities. The risks set out below are not the only risks we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us might also impair our operations and performance. If any of the following events occur, our business, financial condition and results of operations could be materially and adversely affected. In such case, our net asset value and the trading price of our common stock could decline or the value of our other securities may decline, and you may lose all or part of your investment.

Risks Relating to Economic Conditions

Deterioration in the economy and financial markets increases the likelihood of adverse effects on our financial position and results of operations. Such economic adversity could impair our portfolio companies' financial positions and operating results and affect the industries in which we invest, which could, in turn, harm our operating results.

        As a result of the recent recession, the broader fundamentals of the United States economy remain mixed, and unemployment remains elevated. In the event that the United States economy contracts, it is likely that the financial results of small to mid-sized companies, like those in which we invest, could experience deterioration or limited growth from current levels, which could ultimately lead to difficulty in meeting their debt service requirements and an increase in defaults. Consequently, we can provide no assurance that the performance of certain portfolio companies will not be negatively impacted by economic cycles or other conditions, which could also have a negative impact on our future results.

        Although we have been able to secure access to additional liquidity, including through the Credit Facility, periodic follow-on equity offerings, public debt issuances and the leverage available through the SBIC program, the potential for volatility in the debt and equity capital markets provides no assurance that debt or equity capital will be available to us in the future on favorable terms, or at all. Further, if the price of our common stock falls below our net asset value per share, we will be limited in our ability to sell new shares if we do not have shareholder authorization to sell shares at a price below net asset value per share. We have been authorized by our stockholders to sell shares of common stock at a price below our net asset value per share until June 13, 2013, the date of our 2013 Annual Meeting of Stockholders; however, we are not seeking the extension of such shareholder authorization at our 2013 Annual Meeting of Stockholders, but may seek such authorization at future Annual Meetings or Special Meetings of Stockholders.

Risks Relating to Our Business and Structure

Our Investment Portfolio is and will continue to be recorded at fair value, with our Board of Directors having final responsibility for overseeing, reviewing and approving, in good faith, our determination of fair value and, as a result, there is and will continue to be uncertainty as to the value of our portfolio investments.

        Under the 1940 Act, we are required to carry our portfolio investments at market value or, if there is no readily available market value, at fair value as determined by us with our Board of Directors having final responsibility for overseeing, reviewing and approving, in good faith, our determination of fair value. Typically, there is not a public market for the securities of the privately held LMM companies in which we have invested and will generally continue to invest. As a result, we value these securities quarterly at fair value based on inputs from management, a nationally recognized independent advisor (on a rotational basis) and our audit committee with the oversight, review and approval of our Board of Directors. In addition, the market for investments in Middle Market companies is generally not a liquid market, and therefore, we primarily use observable inputs to

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determine the fair value of these investments quarterly through obtaining third party quotes and other independent pricing, which are reviewed by our audit committee with the oversight, review and approval of our Board of Directors. See "Business—Determination of Net Asset Value and Portfolio Valuation Process" for a more detailed description of our valuation process.

        The determination of fair value and consequently, the amount of unrealized gains and losses in our portfolio, are to a certain degree, subjective and dependent on a valuation process approved by our Board of Directors. Certain factors that may be considered in determining the fair value of our investments include external events, such as private mergers, sales and acquisitions involving comparable companies. Because such valuations, and particularly valuations of private securities and private companies, are inherently uncertain, may fluctuate over short periods of time and may be based on estimates, our determinations of fair value may differ materially from the values that would have been used if a ready market for these securities existed. Due to this uncertainty, our fair value determinations may cause our net asset value on a given date to materially understate or overstate the value that we may ultimately realize on one or more of our investments. As a result, investors purchasing our securities based on an overstated net asset value would pay a higher price than the value of our investments might warrant. Conversely, investors selling our securities during a period in which the net asset value understates the value of our investments may receive a lower price for their securities than the value of our investments might warrant.

Our financial condition and results of operations depends on our ability to effectively manage and deploy capital.

        Our ability to achieve our investment objective of maximizing our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity-related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company, depends on our ability to effectively manage and deploy capital, which depends, in turn, on our investment team's ability to identify, evaluate and monitor, and our ability to finance and invest in, companies that meet our investment criteria.

        Accomplishing our investment objective on a cost-effective basis is largely a function of our investment team's handling of the investment process, its ability to provide competent, attentive and efficient services and our access to investments offering acceptable terms. In addition to monitoring the performance of our existing investments, members of our investment team are also called upon, from time to time, to provide managerial assistance to some of our portfolio companies. These demands on their time may distract them or slow the rate of investment.

        Even if we are able to grow and build upon our investment operations, any failure to manage our growth effectively could have a material adverse effect on our business, financial condition, results of operations and prospects. The results of our operations will depend on many factors, including the availability of opportunities for investment, readily accessible short and long-term funding alternatives in the financial markets and economic conditions. Furthermore, if we cannot successfully operate our business or implement our investment policies and strategies as described herein, it could negatively impact our ability to pay dividends.

We may face increasing competition for investment opportunities.

        We compete for investments with other investment funds (including private equity funds, mezzanine funds, BDCs, and SBICs), as well as traditional financial services companies such as commercial banks and other sources of funding. Many of our competitors are substantially larger and have considerably greater financial, technical and marketing resources than we do. For example, some competitors may have a lower cost of capital and access to funding sources that are not available to us. In addition, some of our competitors may have higher risk tolerances or different risk assessments than

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we have. These characteristics could allow our competitors to consider a wider variety of investments, establish more relationships and offer better pricing and more flexible structuring than we are able to do. We may lose investment opportunities if we do not match our competitors' pricing, terms and structure. If we are forced to match our competitors' pricing, terms and structure, we may not be able to achieve acceptable returns on our investments or may bear substantial risk of capital loss. A significant part of our competitive advantage stems from the fact that the market for investments in LMM companies is underserved by traditional commercial banks and other financing sources. A significant increase in the number and/or the size of our competitors in this target market could force us to accept less attractive investment terms. Furthermore, many of our competitors have greater experience operating under, or are not subject to, the regulatory restrictions that the 1940 Act imposes on us as a BDC.

We are dependent upon our key investment personnel for our future success.

        We depend on the members of our investment team, particularly Vincent D. Foster, Todd A. Reppert, Dwayne L. Hyzak, Curtis L. Hartman, David L. Magdol, Nicholas T. Meserve, Robert M. Shuford and Rodger A. Stout for the identification, review, final selection, structuring, closing and monitoring of our investments. These employees have significant investment expertise and relationships that we rely on to implement our business plan. Although we have entered into a non-compete agreement with Mr. Foster, we have no guarantee that he or any other employees will remain employed with us. If we lose the services of these individuals, we may not be able to operate our business as we expect, and our ability to compete could be harmed, which could cause our operating results to suffer.

Our success depends on attracting and retaining qualified personnel in a competitive environment.

        Our growth will require that we retain new investment and administrative personnel in a competitive market. Our ability to attract and retain personnel with the requisite credentials, experience and skills depends on several factors including, but not limited to, our ability to offer competitive wages, benefits and professional growth opportunities. Many of the entities, including investment funds (such as private equity funds and mezzanine funds) and traditional financial services companies, with which we compete for experienced personnel have greater resources than we have.

        The competitive environment for qualified personnel may require us to take certain measures to ensure that we are able to attract and retain experienced personnel. Such measures may include increasing the attractiveness of our overall compensation packages, altering the structure of our compensation packages through the use of additional forms of compensation, or other steps. The inability to attract and retain experienced personnel would have a material adverse effect on our business.

Our business model depends to a significant extent upon strong referral relationships, and our inability to maintain or develop these relationships, as well as the failure of these relationships to generate investment opportunities, could adversely affect our business.

        We expect that members of our management team will maintain their relationships with intermediaries, financial institutions, investment bankers, commercial bankers, financial advisors, attorneys, accountants, consultants and other individuals within our network, and we will rely to a significant extent upon these relationships to provide us with potential investment opportunities. If our management team fails to maintain its existing relationships or develop new relationships with sources of investment opportunities, we will not be able to grow our Investment Portfolio. In addition, individuals with whom members of our management team have relationships are not obligated to provide us with investment opportunities, and, therefore, there is no assurance that such relationships will generate investment opportunities for us.

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There are significant potential conflicts of interest which could impact our investment returns.

        Our executive officers and employees, in their capacities as personnel of the Investment Manager, may manage other investment funds that operate in the same or a related line of business as we do. Accordingly, they may have obligations to such other entities, the fulfillment of which obligations may not be in the best interests of us or our stockholders. In May 2012, we and the Investment Manager executed an investment sub-advisory agreement with HMS Adviser, LP ("HMS Adviser"), which is the investment advisor to HMS Income Fund, Inc. ("HMS Income"), a non-publicly-traded BDC whose registration statement on Form N-2 was declared effective by the SEC in June 2012, to provide certain investment advisory services to HMS Adviser. Under the investment sub-advisory agreement, the Investment Manager is entitled to 50% of the base management fee and the incentive fees earned by HMS Adviser under its advisory agreement with HMS Income. However, the Investment Manager has agreed to waive all such fees through September 30, 2013 to the extent that such fees would cause a portion of any distributions declared and payable by HMS Income to represent a return of capital for purposes of U.S. federal income tax. As a result, as of March 31, 2013, the Investment Manager has not received any base management fee or incentive fees under the investment sub-advisory agreement and the Investment Manager is not due any unpaid compensation for any base management fee or incentive fees under the investment sub-advisory agreement. The sub-advisory relationship requires the Investment Manager to commit resources to achieving HMS Income's investment objective, while such resources were previously solely devoted to achieving our investment objective. Our investment objective and investment strategies are very similar to those of HMS Income and it is likely that an investment appropriate for us or HMS Income would be appropriate for the other entity. As a result, the Investment Manager may face conflicts in allocating investment opportunities between us and HMS Income. Although the Investment Manager will endeavor to allocate investment opportunities in a fair and equitable manner, it is possible that, in the future, we may not be given the opportunity to participate in investments made by other investment funds managed by our officers or employees, such as HMS Income. In any such case, when the Investment Manager identifies an investment, it will be forced to choose which investment fund should make the investment. We have implemented an allocation policy to ensure the equitable distribution of such investment opportunities. We have applied to the SEC for exemptive relief to co-invest with HMS Income, and if the relief is granted, we intend to make such co-investments in accordance with the allocation percentage approved by the independent members of each company's board of directors.

Regulations governing our operation as a BDC will affect our ability to, and the way in which we, raise additional capital.

        Our business will require capital to operate and grow. We may acquire such additional capital from the following sources:

        Senior Securities.     We may issue debt securities or preferred stock and/or borrow money from banks or other financial institutions, which we refer to collectively as senior securities. As a result of issuing senior securities, we will be exposed to additional risks, including the following:

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Under the provisions of the 1940 Act, we are permitted, as a BDC, to issue senior securities only in amounts such that our asset coverage, as defined in the 1940 Act, equals at least 200% immediately after each issuance of senior securities. If the value of our assets declines, we may be unable to satisfy this test. If that happens, we will be prohibited from issuing debt securities or preferred stock and/or borrowing money from banks or other financial institutions and may not be permitted to declare a dividend or make any distribution to stockholders or repurchase shares until such time as we satisfy this test.



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Any amounts that we use to service our debt or make payments on preferred stock will not be available for dividends to our common stockholders.

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It is likely that any senior securities or other indebtedness we issue will be governed by an indenture or other instrument containing covenants restricting our operating flexibility. Additionally, some of these securities or other indebtedness may be rated by rating agencies, and in obtaining a rating for such securities and other indebtedness, we may be required to abide by operating and investment guidelines that further restrict operating and financial flexibility.



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We and, indirectly, our stockholders will bear the cost of issuing and servicing such securities and other indebtedness.



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Preferred stock or any convertible or exchangeable securities that we issue in the future may have rights, preferences and privileges more favorable than those of our common stock, including separate voting rights and could delay or prevent a transaction or a change in control to the detriment of the holders of our common stock.

        Additional Common Stock.     We are not generally able to issue and sell our common stock at a price below net asset value per share. We may, however, sell our common stock, warrants, options or rights to acquire our common stock, at a price below the current net asset value of the common stock if our Board of Directors determines that such sale is in the best interests of our stockholders, and our stockholders approve such sale. See "—Stockholders may incur dilution if we sell shares of our common stock in one or more offerings at prices below the then current net asset value per share of our common stock or issue securities to subscribe to, convert to or purchase shares of our common stock" for a discussion of proposals approved by our stockholders that permit us to issue shares of our common stock below net asset value. We may also make rights offerings to our stockholders at prices per share less than the net asset value per share, subject to applicable requirements of the 1940 Act. If we raise additional funds by issuing more common stock or senior securities convertible into, or exchangeable for, our common stock, the percentage ownership of our stockholders at that time would decrease, and they may experience dilution. Moreover, we can offer no assurance that we will be able to issue and sell additional equity securities in the future, on favorable terms or at all.

The Funds are licensed by the SBA, and therefore subject to SBA regulations.

        MSMF and MSC II, our wholly owned subsidiaries, are licensed to act as SBICs and are regulated by the SBA. The SBA also places certain limitations on the financing terms of investments by SBICs in portfolio companies and prohibits SBICs from providing funds for certain purposes or to businesses in a few prohibited industries. Compliance with SBA requirements may cause the Funds to forego attractive investment opportunities that are not permitted under SBA regulations.

        Further, the SBA regulations require that a licensed SBIC be periodically examined and audited by the SBA to determine its compliance with the relevant SBA regulations. The SBA prohibits, without prior SBA approval, a "change of control" of an SBIC or transfers that would result in any person (or a group of persons acting in concert) owning 10% or more of a class of capital stock of a licensed SBIC. If the Funds fail to comply with applicable SBIC regulations, the SBA could, depending on the severity of the violation, limit or prohibit their use of debentures, declare outstanding debentures immediately due and payable, and/or limit them from making new investments. In addition, the SBA can revoke or suspend a license for willful or repeated violation of, or willful or repeated failure to observe, any provision of the Small Business Investment Act of 1958 or any rule or regulation promulgated thereunder. Such actions by the SBA would, in turn, negatively affect us.

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Because we borrow money, the potential for gain or loss on amounts invested in us is magnified and may increase the risk of investing in us.

        Borrowings, also known as leverage, magnify the potential for loss on investments in our indebtedness and gain or loss on invested equity capital. As we use leverage to partially finance our investments, you will experience increased risks of investing in our securities. We, through the Funds, issue debt securities guaranteed by the SBA and sold in the capital markets. As a result of its guarantee of the debt securities, the SBA has fixed dollar claims on the assets of the Funds that are superior to the claims of our securities holders. We may also borrow from banks and other lenders, including under our Credit Facility, and may issue debt securities or enter into other types of borrowing arrangements in the future. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Capital Resources" for a discussion regarding our Credit Facility. If the value of our assets increases, then leveraging would cause the net asset value attributable to our common stock to increase more sharply than it would have had we not leveraged. Conversely, if the value of our assets decreases, leveraging would cause net asset value to decline more sharply than it otherwise would have had we not leveraged our business. Similarly, any increase in our income in excess of interest payable on the borrowed funds would cause our net investment income to increase more than it would without the leverage, while any decrease in our income would cause net investment income to decline more sharply than it would have had we not borrowed. Such a decline could negatively affect our ability to pay common stock dividends, scheduled debt payments or other payments related to our securities. Leverage is generally considered a speculative investment technique.

        As of March 31, 2013, we, through the Funds, had $225 million of outstanding indebtedness guaranteed by the SBA, which had a weighted average annualized interest cost of approximately 4.8% (exclusive of deferred financing costs). The debentures guaranteed by the SBA have a maturity of ten years, with a current weighted average remaining maturity of 6.1 years as of March 31, 2013, and require semi-annual payments of interest. We will need to generate sufficient cash flow to make required interest payments on the debentures. If we are unable to meet the financial obligations under the debentures, the SBA, as a creditor, will have a superior claim to the assets of the Funds over the holders of our other indebtedness and our stockholders in the event we liquidate or the SBA exercises its remedies under such debentures as the result of a default by us. In addition, as of March 31, 2013, we had $141 million outstanding under our Credit Facility. Borrowings under the Credit Facility bear interest, subject to our election, on a per annum basis equal to (i) the applicable LIBOR rate (0.20% as of March 31, 2013) plus 2.50% or (ii) the applicable base rate (Prime Rate, 3.25% as of March 31, 2013) plus 1.50%. Main Street pays unused commitment fees of 0.375% per annum on the average unused lender commitments under the Credit Facility. If we are unable to meet the financial obligations under the Credit Facility, the Credit Facility lending group will have a superior claim to the assets of MSCC and its subsidiaries (excluding the assets of the Funds) over the holders of our other indebtedness and our stockholders in the event we liquidate or the lending group exercises its remedies under the Credit Facility as the result of a default by us.

        Illustration.    The following table illustrates the effect of leverage on returns from an investment in our common stock assuming various annual returns, net of expenses. The calculations in the table below are hypothetical and actual returns may be higher or lower than those appearing below.

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Assumed Return on Our Portfolio(1)
(net of expenses)

        Our ability to achieve our investment objective may depend in part on our ability to access additional leverage on favorable terms by issuing debentures guaranteed by the SBA, through the Funds, or by borrowing from banks or insurance companies, and there can be no assurance that such additional leverage can in fact be achieved.

Pending legislation may allow us to incur additional leverage.

        As a BDC, under the 1940 Act we generally are not permitted to incur indebtedness unless immediately after such borrowing we have an asset coverage for total borrowings of at least 200% (i.e., the amount of debt may not exceed 50% of the value of our assets). Recent legislation introduced in the U.S. House of Representatives, if passed, would modify this section of the 1940 Act and increase the amount of debt that BDCs may incur by modifying the asset coverage percentage from 200% to 150%. In addition, recent legislation introduced in the U.S. Senate would modify SBA regulations in a manner that may permit us to incur additional SBA leverage. As a result, we may be able to incur additional indebtedness in the future and therefore your risk of an investment in our securities may increase.

We may experience fluctuations in our quarterly results.

        We could experience fluctuations in our quarterly operating results due to a number of factors, including our ability or inability to make investments in companies that meet our investment criteria, the interest rate payable on the debt securities we acquire, the level of portfolio dividend and fee income, the level of our expenses, variations in and the timing of the recognition of realized and unrealized gains or losses, the degree to which we encounter competition in our markets and general economic conditions. As a result of these factors, results for any period should not be relied upon as being indicative of performance in future periods.

Our Board of Directors may change our operating policies and strategies without prior notice or stockholder approval, the effects of which may be adverse.

        Our Board of Directors has the authority to modify or waive our current operating policies, investment criteria and strategies without prior notice and without stockholder approval. We cannot predict the effect any changes to our current operating policies, investment criteria and strategies would have on our business, net asset value, operating results and value of our stock. However, the effects might be adverse, which could negatively impact our ability to pay you dividends and cause you to lose all or part of your investment.

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We will be subject to corporate-level income tax if we are unable to qualify as a RIC under Subchapter M of the Code.

        To maintain RIC tax treatment under the Code, we must meet the following annual distribution, income source and asset diversification requirements:

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The annual distribution requirement for a RIC will be satisfied if we distribute to our stockholders on an annual basis at least 90% of our net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. Depending on the level of taxable income earned in a tax year, we may choose to carry forward taxable income in excess of current year distributions into the next tax year and pay a 4% excise tax on such income. Any such carryover taxable income must be distributed through a dividend declared prior to filing the final tax return related to the year which generated such taxable income. For more information regarding tax treatment, see "Material U.S. Federal Income Tax Considerations—Taxation as a Regulated Investment Company." Because we use debt financing, we are subject to certain asset coverage ratio requirements under the 1940 Act and are (and may in the future become) subject to certain financial covenants under loan and credit agreements that could, under certain circumstances, restrict us from making distributions necessary to satisfy the distribution requirement. If we are unable to obtain cash from other sources, we could fail to qualify for RIC tax treatment and thus become subject to corporate-level income tax.



•

The source income requirement will be satisfied if we obtain at least 90% of our income for each year from dividends, interest, payments with respect to certain securities, loans, gains from the sale of stock or other securities, net income from certain "qualified publicly traded partnerships," or other income derived with respect to our business of investing in such stock or securities.



•

The asset diversification requirement will be satisfied if we meet certain asset diversification requirements at the end of each quarter of our taxable year. To satisfy this requirement, at least 50% of the value of our assets must consist of cash, cash equivalents, U.S. Government securities, securities of other RICs, and other acceptable securities; and no more than 25% of the value of our assets can be invested in the securities, other than U.S. government securities or securities of other RICs, of one issuer, of two or more issuers that are controlled, as determined under applicable Code rules, by us and that are engaged in the same or similar or related trades or businesses or of certain "qualified publicly traded partnerships."

        Failure to meet these requirements may result in our having to dispose of certain investments quickly in order to prevent the loss of RIC status. Because most of our investments will be in private companies, and therefore will be illiquid, any such dispositions could be made at disadvantageous prices and could result in substantial losses. Moreover, if we fail to maintain RIC tax treatment for any reason and are subject to corporate income tax, the resulting corporate taxes could substantially reduce our net assets, the amount of income available for distribution and the amount of our distributions.

We may not be able to pay distributions to our stockholders, our distributions may not grow over time, and a portion of distributions paid to our stockholders may be a return of capital.

        We intend to pay monthly distributions to our stockholders out of assets legally available for distribution. We cannot assure you that we will achieve investment results that will allow us to pay a specified level of cash distributions, previously projected distributions for future periods, or year-to-year increases in cash distributions. Our ability to pay distributions might be adversely affected by, among other things, the impact of one or more of the risk factors described herein. In addition, the inability to satisfy the asset coverage test applicable to us as a BDC could limit our ability to pay distributions. All distributions will be paid at the discretion of our Board of Directors and will depend on our earnings,

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our financial condition, maintenance of our RIC status, compliance with applicable BDC regulations, each of the Funds' compliance with applicable SBIC regulations and such other factors as our Board of Directors may deem relevant from time to time. We cannot assure you that we will pay distributions to our stockholders in the future.

        When we make monthly distributions, we will be required to determine the extent to which such distributions are paid out of current or accumulated earnings, recognized capital gains or capital. To the extent there is a return of capital, investors will be required to reduce their basis in our stock for federal tax purposes, which will result in higher tax liability when the shares are sold, even if they have not increased in value or have lost value. In addition, any return of capital will be net of any sales load and offering expenses associated with sales of shares of our common stock. In the future, our distributions may include a return of capital.

We may have difficulty paying the distributions required to maintain RIC tax treatment under the Code if we recognize income before or without receiving cash representing such income.

        We will include in income certain amounts that we have not yet received in cash, such as: (i) amortization of original issue discount, which may arise if we receive warrants in connection with the origination of a loan such that ascribing a value to the warrants creates original issue discount in the debt instrument or possibly in other circumstances; (ii) contractual payment-in-kind, or PIK, interest, which represents contractual interest added to the loan balance and due at the end of the loan term; (iii) contractual preferred dividends, which represents contractual dividends added to the preferred stock and due at the end of the preferred stock term; or (iv) amortization of market discount, which is associated with loans purchased in the secondary market at a discount to par value. Such amortization of original issue discounts, increases in loan balances as a result of contractual PIK arrangements, cumulative preferred dividends, or amortization of market discount will be included in income before we receive the corresponding cash payments. We also may be required to include in income certain other amounts before we receive such amounts in cash. Investments structured with these features may represent a higher level of credit risk compared to investments generating income which must be paid in cash on a current basis. For the three months ended March 31, 2013, (i) approximately 5.2% of our total investment income was attributable to PIK income not paid currently in cash, (ii) approximately 1.4% of our total investment income was attributable to amortization of original issue discount, (iii) approximately 0.7% of our total investment income was attributable to cumulative dividend income not paid currently in cash, and (iv) approximately 1.4% of our total investment income was attributable to amortization of market discount on loans purchased in the secondary market at a discount. For the year ended December 31, 2012, (i) approximately 4.3% of our total investment income was attributable to PIK income not paid currently in cash, (ii) approximately 2.3% of our total investment income was attributable to amortization of original issue discount, (iii) approximately 0.3% of our total investment income was attributable to cumulative dividend income not paid currently in cash, and (iv) approximately 1.4% of our total investment income was attributable to amortization of market discount on loans purchased in the secondary market at a discount.

        Since, in certain cases, we may recognize income before or without receiving cash representing such income, we may have difficulty meeting the annual distribution requirement necessary to maintain RIC tax treatment under the Code. Accordingly, we may have to sell some of our investments at times and/or at prices we would not consider advantageous, raise additional debt or equity capital or forgo new investment opportunities for this purpose. If we are not able to obtain cash from other sources, we may fail to qualify for RIC tax treatment and thus become subject to corporate-level income tax. For additional discussion regarding the tax implications of a RIC, please see "Material U.S. Federal Income Tax Considerations—Taxation as a Regulated Investment Company."

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We may in the future choose to pay dividends in our own stock, in which case you may be required to pay tax in excess of the cash you receive.

        We may distribute taxable dividends that are payable in part in our stock. Under certain applicable provisions of the Code and the Treasury regulations, distributions payable by us in cash or in shares of stock (at the stockholders election) would satisfy the Annual Distribution Requirement. The IRS has issued private letter rulings providing that a dividend payable in stock or in cash at the election of the stockholders will be treated as a taxable dividend eligible for the dividends paid deduction provided that at least 20% of the total dividend is payable in cash and certain other requirements are satisfied. Taxable stockholders receiving such dividends will be required to include the full amount of the dividend as ordinary income (or as long-term capital gain to the extent such dividend is properly reported as a capital gain dividend) to the extent of our current and accumulated earnings and profits for United States federal income tax purposes. As a result, a U.S. stockholder may be required to pay tax with respect to such dividends in excess of any cash received. If a U.S. stockholder sells the stock it receives as a dividend in order to pay this tax, the sales proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our stock at the time of the sale. Furthermore, with respect to non-U.S. stockholders, we may be required to withhold U.S. tax with respect to such dividends, including in respect of all or a portion of such dividend that is payable in stock. In addition, if a significant number of our stockholders determine to sell shares of our stock in order to pay taxes owed on dividends, it may put downward pressure on the trading price of our stock.

Each of the Funds, as an SBIC, may be unable to make distributions to us that will enable us to meet or maintain RIC status, which could result in the imposition of an entity-level tax.

        In order for us to continue to qualify for RIC tax treatment and to minimize corporate-level taxes, we will be required to distribute substantially all of our net ordinary income and net capital gain income, including income from certain of our subsidiaries, which includes the income from the Funds. We will be partially dependent on the Funds for cash distributions to enable us to meet the RIC distribution requirements. The Funds may be limited by the Small Business Investment Act of 1958, and SBIC regulations governing SBICs, from making certain distributions to us that may be necessary to enable us to maintain our status as a RIC. We may have to request a waiver of the SBA's restrictions for the Funds to make certain distributions to maintain our eligibility for RIC status. We cannot assure you that the SBA will grant such waiver and if the Funds are unable to obtain a waiver, compliance with the SBIC regulations may result in loss of RIC tax treatment and a consequent imposition of an entity-level tax on us.

Because we intend to distribute substantially all of our income to our stockholders to maintain our status as a RIC, we will continue to need additional capital to finance our growth, and regulations governing our operation as a BDC will affect our ability to, and the way in which we, raise additional capital and make distributions.

        In order to satisfy the requirements applicable to a RIC and to minimize corporate-level taxes, we intend to distribute to our stockholders substantially all of our net ordinary income and net capital gain income. We may carry forward excess undistributed taxable income into the next year, net of the 4% excise tax. Any such carryover taxable income must be distributed through a dividend declared prior to filing the final tax return related to the year which generated such taxable income. As a BDC, we generally are required to meet an asset coverage ratio, as defined in the 1940 Act, of at least 200% immediately after each issuance of senior securities. This requirement limits the amount that we may borrow and may prohibit us from making distributions. Because we will continue to need capital to grow our Investment Portfolio, this limitation may prevent us from incurring debt and require us to raise additional equity at a time when it may be disadvantageous to do so.

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        While we expect to be able to borrow and to issue additional debt and equity securities, we cannot assure you that debt and equity financing will be available to us on favorable terms, or at all. In addition, as a BDC, we generally are not permitted to issue equity securities priced below net asset value without stockholder approval. If additional funds are not available to us, we could be forced to curtail or cease new investment activities, and our net asset value could decline.

Stockholders may incur dilution if we sell shares of our common stock in one or more offerings at prices below the then current net asset value per share of our common stock or issue securities to subscribe to, convert to or purchase shares of our common stock.

        The 1940 Act prohibits us from selling shares of our common stock at a price below the current net asset value per share of such stock, with certain exceptions. One such exception is prior stockholder approval of issuances below net asset value provided that our Board of Directors makes certain determinations. In this regard, on June 14, 2012, our common stockholders voted to allow us to issue common stock at a price below net asset value per share for the period ending on June 13, 2013, the date of our 2013 Annual Meeting of Stockholders. Continued access to this exception will require approval of similar proposals at future stockholder meetings. We are not seeking an extension of the shareholder authorization to issue common stock at a price below net asset value per share at our 2013 Annual Meeting of Stockholders because our common stock price per share has been trading significantly above the current net asset value per share of our common stock, but we may seek such authorization at future Annual Meetings or Special Meetings of Stockholders. At our 2008 Annual Meeting of Stockholders, our stockholders approved a proposal to authorize us to issue securities to subscribe to, convert to, or purchase shares of our common stock in one or more offerings. Any decision to sell shares of our common stock below the then current net asset value per share of our common stock or securities to subscribe to, convert to, or purchase shares of our common stock would be subject to the determination by our Board of Directors that such issuance is in our and our stockholders' best interests.

        If we were to sell shares of our common stock below net asset value per share, such sales would result in an immediate dilution to the net asset value per share. This dilution would occur as a result of the sale of shares at a price below the then current net asset value per share of our common stock and a proportionately greater decrease in a stockholder's interest in our earnings and assets and voting interest in us than the increase in our assets resulting from such issuance. In addition, if we issue securities to subscribe to, convert to or purchase shares of common stock, the exercise or conversion of such securities would increase the number of outstanding shares of our common stock. Any such exercise would be dilutive on the voting power of existing stockholders, and could be dilutive with regard to dividends and our net asset value, and other economic aspects of the common stock.

        Because the number of shares of common stock that could be so issued and the timing of any issuance is not currently known, the actual dilutive effect cannot be predicted; however, the example below illustrates the effect of dilution to existing stockholders resulting from the sale of common stock at prices below the net asset value of such shares. Please see "Sales of Common Stock Below Net Asset Value" for a more complete discussion of the potentially dilutive impacts of an offering at a price less than net asset value, or NAV, per share.

        Illustration: Example of Dilutive Effect of the Issuance of Shares Below Net Asset Value.     Assume that Company XYZ has 1,000,000 total shares outstanding, $15,000,000 in total assets and $5,000,000 in total liabilities. The net asset value per share of the common stock of Company XYZ is $10.00. The following table illustrates the reduction to net asset value, or NAV, and the dilution

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experienced by Stockholder A following the sale of 40,000 shares of the common stock of Company XYZ at $9.50 per share, a price below its NAV per share.

Changes in laws or regulations governing our operations may adversely affect our business or cause us to alter our business strategy.

        We, the Funds, and our portfolio companies are subject to applicable local, state and federal laws and regulations, including, without limitation, federal immigration laws and regulations. New legislation may be enacted or new interpretations, rulings or regulations could be adopted, including those governing the types of investments we are permitted to make, any of which could harm us and our stockholders, potentially with retroactive effect. In addition, any change to the SBA's current debenture SBIC program could have a significant impact on our ability to obtain lower-cost leverage, through the Funds, and therefore, our ability to compete with other finance companies.

        Additionally, any changes to the laws and regulations governing our operations relating to permitted investments may cause us to alter our investment strategy in order to avail ourselves of new or different opportunities. Such changes could result in material differences to the strategies and plans set forth herein and may result in our investment focus shifting from the areas of expertise of our investment team to other types of investments in which our investment team may have less expertise or little or no experience. Thus, any such changes, if they occur, could have a material adverse effect on our results of operations and the value of your investment.

Terrorist attacks, acts of war or natural disasters may affect any market for our securities, impact the businesses in which we invest and harm our business, operating results and financial condition.

        Terrorist acts, acts of war or natural disasters may disrupt our operations, as well as the operations of the businesses in which we invest. Such acts have created, and continue to create, economic and political uncertainties and have contributed to global economic instability. Future terrorist activities, military or security operations, or natural disasters could further weaken the domestic/global economies and create additional uncertainties, which may negatively impact the businesses in which we invest directly or indirectly and, in turn, could have a material adverse impact on our business, operating results and financial condition. Losses from terrorist attacks and natural disasters are generally uninsurable.

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Risks Related to Our Investments

Our investments in portfolio companies involve higher levels of risk, and we could lose all or part of our investment.

        Investing in our portfolio companies involves a number of significant risks. Among other things, these companies:

•

may have limited financial resources and may be unable to meet their obligations under their debt instruments that we hold, which may be accompanied by a deterioration in the value of any collateral and a reduction in the likelihood of us realizing any guarantees from subsidiaries or affiliates of our portfolio companies that we may have obtained in connection with our investment, as well as a corresponding decrease in the value of the equity components of our investments;



•

may have shorter operating histories, narrower product lines, smaller market shares and/or significant customer concentrations than larger businesses, which tend to render them more vulnerable to competitors' actions and market conditions, as well as general economic downturns;



•

are more likely to depend on the management talents and efforts of a small group of persons; therefore, the death, disability, resignation, termination, or significant under-performance of one or more of these persons could have a material adverse impact on our portfolio company and, in turn, on us;



•

generally have less predictable operating results, may from time to time be parties to litigation, may be engaged in rapidly changing businesses with products subject to a substantial risk of obsolescence, and may require substantial additional capital to support their operations, finance expansion or maintain their competitive position; and



•

generally have less publicly available information about their businesses, operations and financial condition. We are required to rely on the ability of our management team and investment professionals to obtain adequate information to evaluate the potential returns from investing in these companies. If we are unable to uncover all material information about these companies, we may not make a fully informed investment decision, and may lose all or part of our investment.

        In addition, in the course of providing significant managerial assistance to certain of our portfolio companies, certain of our officers and directors may serve as directors on the boards of such companies. To the extent that litigation arises out of our investments in these companies, our officers and directors may be named as defendants in such litigation, which could result in an expenditure of funds (through our indemnification of such officers and directors) and the diversion of management time and resources.

The lack of liquidity in our investments may adversely affect our business.

        We invest, and will continue to invest in companies whose securities are not publicly traded, and whose securities will be subject to legal and other restrictions on resale or will otherwise be less liquid than publicly traded securities. The illiquidity of these investments may make it difficult for us to sell these investments when desired. In addition, if we are required to liquidate all or a portion of our portfolio quickly, we may realize significantly less than the value at which we had previously recorded these investments. As a result, we do not expect to achieve liquidity in our investments in the near-term. Our investments are usually subject to contractual or legal restrictions on resale or are otherwise illiquid because there is usually no established trading market for such investments. The

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illiquidity of most of our investments may make it difficult for us to dispose of them at a favorable price, and, as a result, we may suffer losses.

We may not have the funds or ability to make additional investments in our portfolio companies.

        We may not have the funds or ability to make additional investments in our portfolio companies. After our initial investment in a portfolio company, we may be called upon from time to time to provide additional funds to such company or have the opportunity to increase our investment through the extension of additional loans, the exercise of a warrant to purchase equity securities, or the funding of additional equity investments. There is no assurance that we will make, or will have sufficient funds to make, follow-on investments. Any decisions not to make a follow-on investment or any inability on our part to make such an investment may have a negative impact on a portfolio company in need of such an investment, may result in a missed opportunity for us to increase our participation in a successful operation or may reduce the expected yield on the investment.

Our portfolio companies may incur debt that ranks equally with, or senior to, our investments in such companies.

        We invest primarily in the secured term debt of LMM and Middle Market companies and equity issued by LMM companies. Our portfolio companies may have, or may be permitted to incur, other debt that ranks equally with, or senior to, the debt in which we invest. By their terms, such debt instruments may entitle the holders to receive payment of interest or principal on or before the dates on which we are entitled to receive payments with respect to the debt instruments in which we invest. Also, in the event of insolvency, liquidation, dissolution, reorganization or bankruptcy of a portfolio company, holders of debt instruments ranking senior to our investment in that portfolio company would typically be entitled to receive payment in full before we receive any distribution. After repaying such senior creditors, such portfolio company may not have any remaining assets to use for repaying its obligation to us. In the case of debt ranking equally with debt instruments in which we invest, we would have to share on an equal basis any distributions with other creditors holding such debt in the event of an insolvency, liquidation, dissolution, reorganization or bankruptcy of the relevant portfolio company.

There may be circumstances where our debt investments could be subordinated to claims of other creditors or we could be subject to lender liability claims.

        Even though we may have structured certain of our investments as secured loans, if one of our portfolio companies were to go bankrupt, depending on the facts and circumstances, and based upon principles of equitable subordination as defined by existing case law, a bankruptcy court could subordinate all or a portion of our claim to that of other creditors and transfer any lien securing such subordinated claim to the bankruptcy estate. The principles of equitable subordination defined by case law have generally indicated that a claim may be subordinated only if its holder is guilty of misconduct or where the senior loan is re-characterized as an equity investment and the senior lender has actually provided significant managerial assistance to the bankrupt debtor. We may also be subject to lender liability claims for actions taken by us with respect to a borrower's business or instances where we exercise control over the borrower. It is possible that we could become subject to a lender's liability claim, including as a result of actions taken in rendering significant managerial assistance or actions to compel and collect payments from the borrower outside the ordinary course of business.

Second priority liens on collateral securing loans that we make to our portfolio companies may be subject to control by senior creditors with first priority liens. If there is a default, the value of the collateral may not be sufficient to repay in full both the first priority creditors and us.

        Certain loans that we make are secured by a second priority security interest in the same collateral pledged by a portfolio company to secure senior debt owed by the portfolio company to commercial

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banks or other traditional lenders. Often the senior lender has procured covenants from the portfolio company prohibiting the incurrence of additional secured debt without the senior lender's consent. Prior to and as a condition of permitting the portfolio company to borrow money from us secured by the same collateral pledged to the senior lender, the senior lender will require assurances that it will control the disposition of any collateral in the event of bankruptcy or other default. In many such cases, the senior lender will require us to enter into an "intercreditor agreement" prior to permitting the portfolio company to borrow from us. Typically the intercreditor agreements we are requested to execute expressly subordinate our debt instruments to those held by the senior lender and further provide that the senior lender shall control: (1) the commencement of foreclosure or other proceedings to liquidate and collect on the collateral; (2) the nature, timing and conduct of foreclosure or other collection proceedings; (3) the amendment of any collateral document; (4) the release of the security interests in respect of any collateral; and (5) the waiver of defaults under any security agreement. Because of the control we may cede to senior lenders under intercreditor agreements we may enter, we may be unable to realize the proceeds of any collateral securing some of our loans.

        Finally, the value of the collateral securing our debt investment will ultimately depend on market and economic conditions, the availability of buyers and other factors. Therefore, there can be no assurance that the proceeds, if any, from the sale or sales of all of the collateral would be sufficient to satisfy the loan obligations secured by our first or second priority liens. There is also a risk that such collateral securing our investments will decrease in value over time, will be difficult to sell in a timely manner, will be difficult to appraise and will fluctuate in value based upon the success of the portfolio company and market conditions. If such proceeds are not sufficient to repay amounts outstanding under the loan obligations secured by our second priority liens, then we, to the extent not repaid from the proceeds of the sale of the collateral, will only have an unsecured claim against the company's remaining assets, if any.

We are a non-diversified investment company within the meaning of the 1940 Act, and therefore we are not limited with respect to the proportion of our assets that may be invested in securities of a single issuer.

        We are classified as a non-diversified investment company within the meaning of the 1940 Act, which means that we are not limited by the 1940 Act with respect to the proportion of our assets that we may invest in securities of a single issuer. To the extent that we assume large positions in the securities of a small number of issuers, our net asset value may fluctuate to a greater extent than that of a diversified investment company as a result of changes in the financial condition or the market's assessment of the issuer. We may also be more susceptible to any single economic or regulatory occurrence than a diversified investment company. Beyond our RIC asset diversification requirements, we do not have fixed guidelines for diversification, and our investments could be concentrated in relatively few portfolio companies.

We generally will not control our portfolio companies.

        We do not, and do not expect to, control the decision making in many of our portfolio companies, even though we may have board representation or board observation rights, and our debt agreements may contain certain restrictive covenants. As a result, we are subject to the risk that a portfolio company in which we invest will make business decisions with which we disagree and the management of such company, as representatives of the holders of their common equity, will take risks or otherwise act in ways that do not serve our interests as debt investors. Due to the lack of liquidity for our investments in non-traded companies, we may not be able to dispose of our interests in our portfolio companies as readily as we would like or at an appropriate valuation. As a result, a portfolio company may make decisions that would decrease the value of our portfolio holdings.

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Defaults by our portfolio companies will harm our operating results.

        A portfolio company's failure to satisfy financial or operating covenants imposed by us or other lenders could lead to non-payment of interest and other defaults and, potentially, termination of its loans and foreclosure on its secured assets, which could trigger cross-defaults under other agreements and jeopardize a portfolio company's ability to meet its obligations under the debt or equity securities that we hold. We may incur expenses to the extent necessary to seek recovery upon default or to negotiate new terms, which may include the waiver of certain financial covenants, with a defaulting portfolio company.

Any unrealized depreciation we experience in our portfolio may be an indication of future realized losses, which could reduce our income and gains available for distribution.

        As a BDC, we are required to carry our investments at market value or, if no market value is ascertainable, at the fair value as determined in good faith by our Board of Directors. Decreases in the market values or fair values of our investments will be recorded as unrealized depreciation. Any unrealized depreciation in our portfolio could be an indication of a portfolio company's inability to meet its repayment obligations to us with respect to affected loans or a potential impairment of the value of affected equity investments. This could result in realized losses in the future and ultimately in reductions of our income and gains available for distribution in future periods.

Prepayments of our debt investments by our portfolio companies could adversely impact our results of operations and reduce our return on equity.

        We are subject to the risk that the investments we make in our portfolio companies may be repaid prior to maturity. When this occurs, we will generally reinvest these proceeds in temporary investments, pending their future investment in new portfolio companies. These temporary investments will typically have substantially lower yields than the debt being prepaid and we could experience significant delays in reinvesting these amounts. Any future investment in a new portfolio company may also be at lower yields than the debt that was repaid. As a result, our results of operations could be materially adversely affected if one or more of our portfolio companies elect to prepay amounts owed to us. Additionally, prepayments could negatively impact our return on equity, which could result in a decline in the market price of our securities.

Changes in interest rates may affect our cost of capital and net investment income.

        Some of our debt investments will bear interest at variable rates and the interest income from these investments could be negatively affected by decreases in market interest rates. In addition, an increase in interest rates would make it more expensive for us to use debt to finance our investments. As a result, a significant increase in market interest rates could increase our cost of capital, which would reduce our net investment income. Also, an increase in interest rates available to investors could make an investment in our securities less attractive than alternative investments, a situation which could reduce the value of our securities. Conversely, a decrease in interest rates may have an adverse impact on our returns by requiring us to seek lower yields on our debt investments and by increasing the risk that our portfolio companies will prepay our debt investments, resulting in the need to redeploy capital at potentially lower rates. A decrease in market interest rates may also adversely impact our returns on idle funds, which would reduce our net investment income.

We may not realize gains from our equity investments.

        Certain investments that we have made in the past and may make in the future include warrants or other equity securities. Investments in equity securities involve a number of significant risks, including the risk of further dilution as a result of additional issuances, inability to access additional capital and

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failure to pay current distributions. Investments in preferred securities involve special risks, such as the risk of deferred distributions, credit risk, illiquidity and limited voting rights. In addition, we may from time to time make non-control, equity investments in portfolio companies. Our goal is ultimately to realize gains upon our disposition of such equity interests. However, the equity interests we receive may not appreciate in value and, in fact, may decline in value. Accordingly, we may not be able to realize gains from our equity interests, and any gains that we do realize on the disposition of any equity interests may not be sufficient to offset any other losses we experience. We also may be unable to realize any value if a portfolio company does not have a liquidity event, such as a sale of the business, recapitalization or public offering, which would allow us to sell the underlying equity interests. We often seek puts or similar rights to give us the right to sell our equity securities back to the portfolio company issuer; however, we may be unable to exercise these puts rights for the consideration provided in our investment documents if the issuer is in financial distress.

Our Marketable securities and idle funds investments are subject to risks similar to our portfolio company investments.

        Marketable securities and idle funds investments can include, among other things, secured and unsecured debt investments, independently rated debt investments and diversified bond funds. Many of these investments in debt obligations are, or would be if rated, below investment grade quality. Indebtedness of below investment grade quality is regarded as having predominantly speculative characteristics with respect to the issuer's capacity to pay interest and repay principal, similar to our portfolio investments in our portfolio companies. See "—Our investments in portfolio companies involve higher levels of risk, and we could lose all or part of our investment." Many of these Marketable securities and idle funds investments are purchased through over the counter or other markets and are therefore liquid at the time of purchase but may subsequently become illiquid due to events relating to the issuer of the securities, market events, economic conditions or investor perceptions. See "—The lack of liquidity in our investments may adversely affect our business" for a description of risks related to holding illiquid investments. In addition, domestic and foreign markets are complex and interrelated, so that events in one sector of the world markets or economy, or in one geographical region, can reverberate and have materially negative consequences for other market, economic or regional sectors in a manner that may not be foreseen and which may materially affect the market price of our Marketable securities and idle funds investments. Other risks that our portfolio investments are subject to are also applicable to these Marketable securities and idle funds investments.

Our investments in foreign securities may involve significant risks in addition to the risks inherent in U.S. investments.

        Our investments in foreign securities may involve significant risks in addition to the risks inherent in investments in U.S. securities. Our investment strategy contemplates potential investments in debt securities of foreign companies. Investing in foreign companies may expose us to additional risks not typically associated with investing in securities of U.S. companies. These risks include changes in exchange control regulations, political and social instability, expropriation, imposition of foreign taxes, less liquid markets and less available information than is generally the case in the United States, higher transaction costs, less government supervision of exchanges, brokers and issuers, less developed bankruptcy laws, difficulty in enforcing contractual obligations, lack of uniform accounting and auditing standards and greater price volatility.

        Although most of our investments will be U.S. dollar denominated, any investments denominated in a foreign currency will be subject to the risk that the value of a particular currency will change in relation to one or more other currencies. Among the factors that may affect currency values are trade balances, the level of short-term interest rates, differences in relative values of similar assets in

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different currencies, long-term opportunities for investment and capital appreciation, and political developments.

Risks Relating to Our Securities

Shares of closed-end investment companies, including BDCs, may trade at a discount to their net asset value.

        Shares of closed-end investment companies, including BDCs, may trade at a discount to net asset value. This characteristic of closed-end investment companies and BDCs is separate and distinct from the risk that our net asset value per share may decline. We cannot predict whether our common stock will trade at, above or below net asset value. In addition, if our common stock trades below net asset value, we will generally not be able to issue additional common stock at the market price unless our stockholders approve such a sale and our Board of Directors makes certain determinations. See "—Risks Relating to Our Business and Structure—Stockholders may incur dilution if we sell shares of our common stock in one or more offerings at prices below the then current net asset value per share of our common stock or issue securities to subscribe to, convert to or purchase shares of our common stock" for a discussion of a proposal approved by our stockholders that permits us to issue shares of our common stock below net asset value.

We may be unable to invest a significant portion of the net proceeds from an offering or from exiting an investment or other capital on acceptable terms, which could harm our financial condition and operating results.

        Delays in investing the net proceeds raised in an offering or from exiting an investment or other capital may cause our performance to be worse than that of other fully invested BDCs or other lenders or investors pursuing comparable investment strategies. We cannot assure you that we will be able to identify any investments that meet our investment objective or that any investment that we make will produce a positive return. We may be unable to invest the net proceeds of any offering or from exiting an investment or other capital on acceptable terms within the time period that we anticipate or at all, which could harm our financial condition and operating results.

        We anticipate that, depending on market conditions and the amount of the capital, it may take us a substantial period of time to invest substantially all the capital in securities meeting our investment objective. During this period, we will invest the capital primarily in Marketable securities and idle funds investments, which may produce returns that are significantly lower than the returns which we expect to achieve when our portfolio is fully invested in securities meeting our investment objective. As a result, any distributions that we pay during such period may be substantially lower than the distributions that we may be able to pay when our portfolio is fully invested in securities meeting our investment objective. In addition, until such time as the net proceeds of any offering or from exiting an investment or other capital are invested in new securities meeting our investment objective, the market price for our securities may decline. Thus, the initial return on your investment may be lower than when, if ever, our portfolio is fully invested in securities meeting our investment objective.

Investing in our securities may involve an above average degree of risk.

        The investments we make in accordance with our investment objective may result in a higher amount of risk than alternative investment options and a higher risk of volatility or loss of principal. Our investments in portfolio companies involve higher levels of risk, and therefore, an investment in our securities may not be suitable for someone with lower risk tolerance.

The market price of our securities may be volatile and fluctuate significantly.

        Fluctuations in the trading prices of our securities may adversely affect the liquidity of the trading market for our securities and, if we seek to raise capital through future securities offerings, our ability

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to raise such capital. The market price and liquidity of the market for our securities may be significantly affected by numerous factors, some of which are beyond our control and may not be directly related to our operating performance. These factors include:

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significant volatility in the market price and trading volume of securities of BDCs or other companies in our sector, which are not necessarily related to the operating performance of these companies;



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changes in regulatory policies, accounting pronouncements or tax guidelines, particularly with respect to RICs, BDCs or SBICs;



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inability to obtain any exemptive relief that may be required by us in the future from the SEC;



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loss of our BDC or RIC status or either of the Funds' status as an SBIC;



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changes in our earnings or variations in our operating results;



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changes in the value of our portfolio of investments;



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any shortfall in our investment income or net investment income or any increase in losses from levels expected by investors or securities analysts;



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loss of a major funding source;



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fluctuations in interest rates;



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the operating performance of companies comparable to us;



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departure of our key personnel;



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global or national credit market changes; and



•

general economic trends and other external factors.

Provisions of the Maryland General Corporation Law and our articles of incorporation and bylaws could deter takeover attempts and have an adverse impact on the price of our common stock.

        The Maryland General Corporation Law and our articles of incorporation and bylaws contain provisions that may have the effect of discouraging, delaying or making difficult a change in control of our company or the removal of our incumbent directors. The existence of these provisions, among others, may have a negative impact on the price of our common stock and may discourage third-party bids for ownership of our company. These provisions may prevent any premiums being offered to you for our common stock.

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CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS

        Some of the statements in this prospectus and any accompanying prospectus supplement constitute forward-looking statements because they relate to future events or our future performance or financial condition. The forward-looking statements contained in this prospectus and any accompanying prospectus supplement may include statements as to:

•

our future operating results and dividend projections;



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our business prospects and the prospects of our portfolio companies;



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the impact of the investments that we expect to make;



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the ability of our portfolio companies to achieve their objectives;



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our expected financings and investments;



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the adequacy of our cash resources and working capital; and



•

the timing of cash flows, if any, from the operations of our portfolio companies.

        In addition, words such as "anticipate," "believe," "expect" and "intend" indicate a forward-looking statement, although not all forward-looking statements include these words. The forward-looking statements contained in this prospectus and any accompanying prospectus supplement involve risks and uncertainties. Our actual results could differ materially from those implied or expressed in the forward-looking statements for any reason, including the factors set forth in "Risk Factors" and elsewhere in this prospectus and any accompanying prospectus supplement. Other factors that could cause actual results to differ materially include:

•

changes in the economy;



•

risks associated with possible disruption in our operations or the economy generally due to terrorism or natural disasters; and



•

future changes in laws or regulations and conditions in our operating areas.

        We have based the forward-looking statements included in this prospectus and will base the forward-looking statements included in any accompanying prospectus supplement on information available to us on the date of this prospectus and any accompanying prospectus supplement, as appropriate, and we assume no obligation to update any such forward-looking statements, except as required by law. Although we undertake no obligation to revise or update any forward-looking statements, whether as a result of new information, future events or otherwise, you are advised to consult any additional disclosures that we may make directly to you, including in the form of a prospectus supplement or post-effective amendment to the registration statement, or through reports that we in the future may file with the SEC, including annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K.

USE OF PROCEEDS

        We intend to use the net proceeds from any offering to make investments in accordance with our investment objective and strategies described in this prospectus or any prospectus supplement, to make investments in marketable securities and idle funds investments, which may include investments in secured intermediate term bank debt, rated debt securities and other income producing investments, to pay our operating expenses and other cash obligations, and for general corporate purposes. Our ability to achieve our investment objective may be limited to the extent that the net proceeds from an offering, pending full investment, are held in interest-bearing deposits or other short-term instruments. See "Risk Factors—Risks Relating to Our Securities—We may be unable to invest a significant portion of the net proceeds from an offering or from exiting an investment or other capital on acceptable terms, which could harm our financial condition and operating results." The supplement to this prospectus relating to an offering will more fully identify the use of proceeds from such an offering.

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PRICE RANGE OF COMMON STOCK AND DISTRIBUTIONS

        Our common stock is traded on the New York Stock Exchange ("NYSE") under the symbol "MAIN." Prior to October 14, 2010, our common stock was traded on the NASDAQ Global Select Market under the same symbol "MAIN." Our common stock began trading on the NASDAQ Global Select Market on October 5, 2007. Prior to that date, there was no established public trading market for our common stock.

        The following table sets forth, for each fiscal quarter during 2013, 2012 and 2011, the range of high and low closing prices of our common stock as reported on the NYSE, and the sales price as a percentage of the net asset value per share of our common stock.

        On July 30, 2013 the last sale price of our common stock on the NYSE was $30.80 per share, and there were approximately 206 holders of record of the common stock which did not include shareholders for whom shares are held in "nominee" or "street name." The net asset value per share of our common stock on March 31, 2013 (the last date prior to the date of this prospectus on which we determined our net asset value per share) was $18.55, and the July 30, 2013 closing price of our common stock was 166% of this net asset value per share.

        Shares of BDCs may trade at a market price that is less than the value of the net assets attributable to those shares. The possibility that our shares of common stock will trade at a discount from net asset value per share or at premiums that are unsustainable over the long term are separate and distinct from the risk that our net asset value per share will decrease. It is not possible to predict whether our common stock will trade at, above, or below net asset value per share. Since our IPO in October 2007, our shares of common stock have traded at prices both less than and exceeding our net asset value per share.

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        We currently pay monthly dividends to our stockholders. Our monthly dividends, if any, will be determined by our Board of Directors on a quarterly basis. In addition to our monthly dividends, in January 2013 we began paying periodic supplemental dividends out of our undistributed taxable income, or spillover income. Our future supplemental dividends, if any, will be determined by our Board of Directors on a periodic basis.

        The following table summarizes our dividends declared to date:

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        To obtain and maintain RIC tax treatment, we must, among other things, distribute at least 90% of our net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. We will be subject to a 4% nondeductible federal excise tax on certain undistributed taxable income unless we distribute in a timely manner an amount at least equal to the sum of (1) 98% of our net ordinary income for each calendar year, (2) 98.2% of our capital gain net income for the one-year period ending December 31 in that calendar year and (3) any income recognized, but not distributed, in preceding years (the "Excise Tax Avoidance Requirement"). Dividends declared and paid by us in a year will generally differ from taxable income for that year, as such dividends may include the distribution of current year taxable income, less amounts carried over into the following year, and the distribution of prior year taxable income carried over into and distributed in the current year. For amounts we carry over into the following year, we will be required to pay a 4% excise tax for the excess over 98% of our annual taxable income in excess of distributions for the year. We may retain for investment some or all of our net capital gains (i.e., realized net long-term capital gains in excess of realized net short-term capital losses) and treat such amounts as deemed distributions to our stockholders. If we do this, our stockholders will be treated as if they had received actual distributions of the capital gains we retained and then reinvested the net after-tax proceeds in our common stock. In general, our stockholders also would be eligible to claim a tax credit (or, in certain circumstances, a tax refund) equal to their allocable shares of the tax we paid on the capital gains deemed distributed to them. We can offer no assurance that we will achieve results that will permit the payment of any cash distributions and, if we issue senior securities, we may be prohibited from making distributions if doing so causes us to fail to maintain the asset coverage ratios stipulated by the 1940 Act or if distributions are limited by the terms of any of our borrowings.

        We may distribute taxable dividends that are payable in part in our stock. Under certain applicable provisions of the Code and the Treasury regulations, distributions payable by us in cash or in shares of stock (at the stockholders election) would satisfy the Annual Distribution Requirement. The IRS has issued private letter rulings providing that a dividend payable in stock or in cash at the election of the stockholders will be treated as a taxable dividend eligible for the dividends paid deduction provided that at least 20% of the total dividend is payable in cash and certain other requirements are satisfied. Taxable stockholders receiving such dividends will be required to include the full amount of the dividend as ordinary income (or as long-term capital gain to the extent such dividend is properly reported as a capital gain dividend), to the extent of our current and accumulated earnings and profits for United States federal income tax purposes. As a result, a U.S. stockholder may be required to pay tax with respect to such dividends in excess of any cash received. If a U.S. stockholder sells the stock it receives as a dividend in order to pay this tax, the sales proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our stock at the time of the sale. Furthermore, with respect to non-U.S. stockholders, we may be required to withhold U.S. tax with respect to such dividends, including in respect of all or a portion of such dividend that is payable in stock. In addition, if a significant number of our stockholders determine to sell shares of our stock in order to pay taxes owed on dividends, it may put downward pressure on the trading price of our stock.

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RATIOS OF EARNINGS TO FIXED CHARGES

        The following table contains our ratio of earnings to fixed charges for the periods indicated, computed as set forth below. You should read these ratios of earnings to fixed charges in connection with our consolidated financial statements, including the notes to those statements, included in this prospectus.

        For purposes of computing the ratios of earnings to fixed charges, earnings represent net increase in net assets resulting from operations plus (or minus) income tax expense (benefit) including excise tax expense plus fixed charges. Fixed charges include interest and credit facility fees expense and amortization of debt issuance costs.

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SELECTED FINANCIAL DATA

        The selected financial and other data below reflects the consolidated financial condition and the consolidated statement of operations of Main Street and its subsidiaries as of and for the years ended December 31, 2012, 2011, 2010, 2009 and 2008, as of March 31, 2013 and for the three months ended March 31, 2013 and 2012. The selected financial data at December 31, 2012, 2011, 2010, 2009 and 2008 and for the years ended December 31, 2012, 2011, 2010, 2009 and 2008, have been derived from consolidated financial statements that have been audited by Grant Thornton LLP, an independent registered public accounting firm. The selected financial data at March 31, 2013, and for the three months ended March 31, 2013 and 2012, have been derived from unaudited financial data but, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary to present fairly the financial condition and operating results for such interim periods. Interim results as of and for the three months ended March 31, 2013 are not necessarily indicative of the results that may be expected for the year ending December 31, 2013. You should read this selected financial data in conjunction with our "Management's Discussion and Analysis of Financial Condition and Results of Operations," "Senior Securities" and the financial statements and related notes included in this prospectus.

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MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS

        The following discussion should be read in conjunction with our financial statements and the notes thereto included elsewhere in this prospectus.

        Statements we make in the following discussion which express a belief, expectation or intention, as well as those that are not historical fact, are forward-looking statements that are subject to risks, uncertainties and assumptions. Our actual results, performance or achievements, or industry results, could differ materially from those we express in the following discussion as a result of a variety of factors, including the risks and uncertainties we have referred to under the headings "Cautionary Statement Concerning Forward-Looking Statements" and "Risk Factors" in this prospectus.

ORGANIZATION

        Main Street Capital Corporation ("MSCC") was formed on March 9, 2007 for the purpose of (i) acquiring 100% of the equity interests of Main Street Mezzanine Fund, LP ("MSMF") and its general partner, Main Street Mezzanine Management, LLC ("MSMF GP"), (ii) acquiring 100% of the equity interests of Main Street Capital Partners, LLC (the "Investment Manager"), (iii) raising capital in an initial public offering, which was completed in October 2007 (the "IPO"), and (iv) thereafter operating as an internally managed business development company ("BDC") under the Investment Company Act of 1940, as amended (the "1940 Act"). MSMF is licensed as a Small Business Investment Company ("SBIC") by the United States Small Business Administration ("SBA") and the Investment Manager acts as MSMF's manager and investment adviser. Because the Investment Manager, which employs all of the executive officers and other employees of MSCC, is wholly owned by us, we do not pay any external investment advisory fees, but instead we incur the operating costs associated with employing investment and portfolio management professionals through the Investment Manager. The IPO and related transactions discussed above were consummated in October 2007 and are collectively termed the "Formation Transactions."

        On January 7, 2010, MSCC consummated transactions (the "Exchange Offer") to exchange 1,239,695 shares of its common stock for approximately 88% of the total dollar value of the limited partner interests in Main Street Capital II, LP ("MSC II" and, together with MSMF, the "Funds"). Pursuant to the terms of the Exchange Offer, 100% of the membership interests in the general partner of MSC II, Main Street Capital II GP, LLC ("MSC II GP"), were also transferred to MSCC for no consideration. MSC II commenced operations in January 2006, is an investment fund that operates as an SBIC and is also managed by the Investment Manager. During the first quarter of 2012, MSCC exchanged 229,634 shares of its common stock to acquire all of the remaining minority ownership in the total dollar value of the MSC II limited partnership interests, including approximately 5% owned by affiliates of MSCC (the "Final MSC II Exchange"). After the completion of the Final MSC II Exchange, MSCC owns 100% of MSC II. The Exchange Offer and related transactions, including the transfer of the MSC II GP interests and the Final MSC II Exchange, are collectively termed the "Exchange Offer Transactions."

        MSCC has elected to be treated for federal income tax purposes as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). As a result, MSCC generally will not pay corporate-level federal income taxes on any net ordinary income or capital gains that it distributes to its stockholders as dividends.

        MSCC has direct and indirect wholly owned subsidiaries that have elected to be taxable entities (the "Taxable Subsidiaries"). The primary purpose of these entities is to hold certain investments that generate "pass through" income for tax purposes. The Taxable Subsidiaries are each taxed at their normal corporate tax rates based on their taxable income.

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        Unless otherwise noted or the context otherwise indicates, the terms "we," "us," "our" and "Main Street" refer to MSCC and its consolidated subsidiaries, which include the Funds and the Taxable Subsidiaries.

OVERVIEW

        We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies and debt capital to middle market ("Middle Market") companies. Our portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies that operate in diverse industry sectors. We seek to partner with entrepreneurs, business owners and management teams and generally provide "one stop" financing alternatives within our LMM portfolio. We invest primarily in secured debt investments, equity investments, warrants and other securities of LMM companies based in the United States and in secured debt investments of Middle Market companies generally headquartered in the United States. Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million.

        Our private loan ("Private Loan") investments are made in businesses that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. The structure, terms and conditions for these Private Loan investments are typically consistent with the structure, terms and conditions for the loans made in our LMM portfolio or Middle Market portfolio.

        Our other portfolio ("Other Portfolio") investments primarily consist of investments which are not consistent with the typical profiles for our LMM, Middle Market or Private Loan portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

        We seek to fill the current financing gap for LMM businesses, which, historically, have had more limited access to financing from commercial banks and other traditional sources. The underserved nature of the LMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a company's capital structure, from senior secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing options, or a "one stop" financing solution. Providing customized, "one stop" financing solutions has become even more relevant to our LMM portfolio companies in the current investing environment. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our investments. Our LMM portfolio debt investments are generally secured by a first lien on the assets of the portfolio company and typically have a term of between five and seven years. We believe that our LMM investment strategy has a lower correlation to the broader debt and equity markets.

        As of March 31, 2013, we had debt and equity investments in 57 LMM portfolio companies with an aggregate fair value of approximately $520.3 million, with a total cost basis of approximately $412.2 million, and a weighted average annual effective yield on our LMM debt investments of approximately

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14.2%. As of March 31, 2013 approximately 76% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 93% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At March 31, 2013, we had equity ownership in approximately 93% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 33%. As of December 31, 2012, Main Street had debt and equity investments in 56 LMM portfolio companies with an aggregate fair value of approximately $482.9 million, with a total cost basis of approximately $380.5 million, and a weighted average annual effective yield on our LMM debt investments of approximately 14.3%. As of December 31, 2012, approximately 75% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 93.0% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2012, we had equity ownership in approximately 93% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 33%. The weighted average annual yields were computed using the effective interest rates for all debt investments at March 31, 2013 and December 31, 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt instruments and any debt investments on non-accrual status.

        We also pursue investments in Middle Market companies. Our Middle Market portfolio investments primarily consist of direct or secondary purchases of interest-bearing debt securities in privately held companies that are generally larger in size than the LMM companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the company and have an expected duration of between three and five years.

        As of March 31, 2013, we had Middle Market portfolio investments in 80 companies, collectively totaling approximately $361.9 million in fair value with a total cost basis of approximately $354.4 million. The weighted average revenue for the 80 Middle Market portfolio company investments was approximately $557.0 million as of March 31, 2013. As of March 31, 2013, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 91% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 8.2% as of March 31, 2013. As of December 31, 2012, we had Middle Market portfolio investments in 79 companies, collectively totaling approximately $352.0 million in fair value with a total cost basis of approximately $348.1 million. The weighted average revenue for the 79 Middle Market portfolio company investments was approximately $533.6 million as of December 31, 2012. As of December 31, 2012, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 91% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 8.0% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at March 31, 2013 and December 31, 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt instruments.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of the companies included in our LMM portfolio or our Middle Market portfolio. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have a term of between three and seven years.

        As of March 31, 2013, we had Private Loan portfolio investments in 10 companies, collectively totaling approximately $74.5 million in fair value with a total cost basis of approximately $73.8 million. The weighted average revenue for the 10 Private Loan portfolio company investments was

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approximately $193.8 million as of March 31, 2013. As of March 31, 2013, 99% of our Private Loan portfolio investments were in the form of debt investments and all such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 14.0% as of March 31, 2013. As of December 31, 2012, we had Private Loan portfolio investments in 9 companies, collectively totaling approximately $65.5 million in fair value with a total cost basis of approximately $64.9 million. The weighted average revenue for the 9 Private Loan portfolio company investments was approximately $230.5 million as of March 31, 2013. As of December 31, 2012, 99% of our Private Loan portfolio investments were in the form of debt investments and all such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 14.8% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at March 31, 2013 and December 31, 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt instruments.

        As of March 31, 2013, we had Other Portfolio investments in 4 companies, collectively totaling approximately $28.7 million in fair value and approximately $27.9 million in cost basis and which comprised 2.9% of our Investment Portfolio at fair value as of March 31, 2013. As of December 31, 2012, we had Other Portfolio investments in 3 companies, collectively totaling approximately $24.1 million in both fair value and approximately $23.6 million in cost basis and which comprised 2.6% of our Investment Portfolio at fair value as of December 31, 2012.

        During the three months ended March 31, 2013, there were nine portfolio company investment transfers from the LMM and Middle Market portfolio investment categories to the Private Loan portfolio investment category totaling $65.5 million at fair value and $64.9 million at cost as of December 31, 2012.

        Our portfolio investments are generally made through MSCC and the Funds. MSCC and the Funds share the same investment strategies and criteria, although they are subject to different regulatory regimes. An investor's return in MSCC will depend, in part, on the Funds' investment returns as MSMF and MSC II are both wholly owned subsidiaries of MSCC.

        The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria, and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long-term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation will also fluctuate depending upon portfolio activity and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results.

        MSCC and its consolidated subsidiaries are internally managed by the Investment Manager, a wholly owned subsidiary of MSCC, which employs all of the executive officers and other employees of Main Street. Because the Investment Manager is wholly owned by MSCC, Main Street does not pay any external investment advisory fees, but instead incurs the operating costs associated with employing investment and portfolio management professionals through the Investment Manager. We believe that our internally managed structure provides us with a beneficial operating expense structure when compared to other publicly-traded and privately-held investment firms which are externally managed,

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and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our Investment Portfolio. For the three months ended March 31, 2013 and 2012, the ratio of our total operating expenses, excluding interest expense, as a percentage of our quarterly average total assets was 1.7% and 2.0%, respectively, on an annualized basis, and 1.8% for the year ended December 31, 2012.

        During May 2012, MSCC and the Investment Manager executed an investment sub-advisory agreement with HMS Adviser, LP ("HMS Adviser"), which is the investment advisor to HMS Income Fund, Inc. ("HMS Income"), a non publicly-traded BDC whose registration statement on Form N-2 was declared effective by the SEC in June 2012, to provide certain investment advisory services to HMS Adviser. MSCC is initially providing such investment advisory services to HMS Adviser, but it is ultimately intended that the Investment Manager will provide such services because the fees MSCC receives from such arrangement could otherwise have negative consequences on its ability to meet the source-of-income requirement necessary for it to maintain its RIC tax treatment (MSCC or the Investment Adviser, whichever is providing such investment advisory services, the "Sub-Adviser"). Certain relief must be obtained from the SEC before the Investment Manager is permitted to provide these services to HMS Adviser, which relief is being sought, but there can be no assurance that it will be obtained. Under the investment sub-advisory agreement, the Sub-Adviser is entitled to 50% of the base management fee and the incentive fees earned by HMS Adviser under its advisory agreement with HMS Income. However, the Sub-Adviser has agreed to waive all such fees from the effective date of HMS Adviser's registration statement on Form N-2 through September 30, 2013 to the extent that such fees would cause a portion of any distributions declared and payable by HMS Income to represent a return of capital for purposes of U.S. federal income tax. As a result, as of March 31, 2013, the Sub-Adviser has not received any base management fee or incentive fees under the investment sub-advisory agreement and the Sub-Adviser is not due any unpaid compensation for any base management fee or incentive fees under the investment sub-advisory agreement.

CRITICAL ACCOUNTING POLICIES

Basis of Presentation

        Our financial statements are prepared in accordance with generally accepted accounting principles in the United States of America ("U.S. GAAP"). For the three months ended March 31, 2013 and 2012, our consolidated financial statements include the accounts of MSCC and its consolidated subsidiaries, which include the Funds and the Taxable Subsidiaries. The Investment Portfolio, as used herein, refers to all of our LMM portfolio investments, Middle Market portfolio investments, Private Loan portfolio investments, Other Portfolio investments and the investment in the "Investment Manager." Marketable securities and idle funds investments are classified as financial instruments and are reported separately on our Consolidated Balance Sheets and Consolidated Schedule of Investments due to the nature of such investments. Our results of operations and cash flows for the three months ended March 31, 2013 and 2012 and financial position as of March 31, 2013 and December 31, 2012, are presented on a consolidated basis. The effects of all intercompany transactions between Main Street and its consolidated subsidiaries have been eliminated in consolidation. Certain reclassifications have been made to prior period balances to conform with the current presentation, including certain investments previously included as part of the LMM portfolio or Middle Market portfolio that are now classified as part of the Private Loan portfolio and the reclassification of Investment Portfolio and Marketable securities and idle funds investment related activity from cash flows from investing activities to cash flows from operating activities.

        The accompanying unaudited consolidated financial statements of Main Street are presented in conformity with U.S. GAAP for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Article 10 of Regulation S-X. Accordingly, certain disclosures accompanying annual financial statements prepared in accordance with U.S. GAAP are omitted. In the

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opinion of management, the unaudited consolidated financial results included herein contain all adjustments, consisting solely of normal recurring accruals, considered necessary for the fair presentation of financial statements for the interim periods included herein. The results of operations for the three months ended March 31, 2013 are not necessarily indicative of the operating results to be expected for the full year. Also, the unaudited financial statements and notes should be read in conjunction with the audited financial statements and notes thereto for the year ended December 31, 2012. Financial statements prepared on a U.S. GAAP basis require management to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements and accompanying notes. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed herein.

        Under the investment company rules and regulations pursuant to Article 6 of Regulation S-X and the Audit and Accounting Guide for Investment Companies issued by the American Institute of Certified Public Accountants (the "AICPA Guide"), we are precluded from consolidating portfolio company investments, including those in which we have a controlling interest, unless the portfolio company is another investment company. An exception to this general principle in the AICPA Guide occurs if we own a controlled operating company that provides all or substantially all of its services directly to us, or to an investment company of ours. None of the investments made by us qualify for this exception. Therefore, the Investment Portfolio is carried on the balance sheet at fair value, as discussed further in Note B to our consolidated financial statements, with any adjustments to fair value recognized as "Net Change in Unrealized Appreciation (Depreciation)" on our Statement of Operations until the investment is realized, usually upon exit, resulting in any gain or loss being recognized as a "Net Realized Gain (Loss) from Investments."

Portfolio Investment Valuation

        The most significant determination inherent in the preparation of our consolidated financial statements is the valuation of our Investment Portfolio and the related amounts of unrealized appreciation and depreciation. As of March 31, 2013 and December 31, 2012, approximately 96% and 89%, respectively, of our total assets at each date represented investments in portfolio companies valued at fair value (including our investment in the Investment Manager). We are required to report our investments at fair value. We follow the provisions of the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("Codification" or "ASC") 820, Fair Value Measurements and Disclosures ("ASC 820"). ASC 820 defines fair value, establishes a framework for measuring fair value, establishes a fair value hierarchy based on the quality of inputs used to measure fair value, and enhances disclosure requirements for fair value measurements.

        Our business strategy calls for us to invest primarily in illiquid debt and equity securities issued by private, LMM companies and debt securities issued by Middle Market companies that are generally larger in size than the LMM companies. We also categorize some of our investments in LMM companies and Middle Market companies as Private Loan portfolio investments, which are typically debt securities issued by companies that are consistent in size with either the LMM companies or Middle Market companies, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Our portfolio also includes Other Portfolio investments which primarily consist of investments which are not consistent with the typical profiles for our LMM portfolio investments, Middle Market portfolio investments or Private Loan portfolio investments, including investments which may be managed by third parties. All of these portfolio investments may be subject to restrictions on resale.

        LMM investments and Other Portfolio investments generally have no established trading market while Middle Market securities generally have established markets that are not active. Private Loan investments may include investments which have no established trading market or have established markets that are not active. We determine in good faith the fair value of our Investment Portfolio

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pursuant to a valuation policy in accordance with ASC 820 and a valuation process approved by our Board of Directors and in accordance with the 1940 Act. Our valuation policy and process is intended to provide a consistent basis for determining the fair value of our portfolio.

        For LMM investments, we review external events, including private mergers, sales and acquisitions involving comparable companies, and include these events in the valuation process. For Middle Market portfolio investments, we primarily use observable inputs such as quoted prices in the valuation process. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we generally use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        For valuation purposes, "control" LMM portfolio investments are composed of debt and equity securities in companies for which we have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for our control LMM portfolio investments. As a result, for control LMM portfolio investments, we determine the fair value using a combination of market and income approaches. Under the market approach, we will typically use the enterprise value methodology to determine the fair value of these investments. The enterprise value is the fair value at which an enterprise could be sold in a transaction between two willing parties, other than through a forced or liquidation sale. Typically, private companies are bought and sold based on multiples of earnings before interest, taxes, depreciation and amortization, or EBITDA, cash flows, net income, revenues, or in limited cases, book value. There is no single methodology for estimating enterprise value. For any one portfolio company, enterprise value is generally described as a range of values from which a single estimate of enterprise value is derived. In estimating the enterprise value of a portfolio company, we analyze various factors, including the portfolio company's historical and projected financial results. We allocate the enterprise value to investments in order of the legal priority of the various components of the portfolio company's capital structure. We will also use the income approach to determine the fair value of these securities, based on projections of the discounted future free cash flows that the portfolio company or the debt security will likely generate, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments.. The valuation approaches for our control LMM portfolio investments estimate the value of the investment if we were to sell, or exit, the investment. In addition, these valuation approaches consider the value associated with our ability to control the capital structure of the portfolio company, as well as the timing of a potential exit.

        For valuation purposes, "non-control" LMM portfolio investments are composed of debt and equity securities in companies for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for non-control LMM portfolio investments. For our non-control LMM investments, we use a combination of the market and income approaches to value our equity investments and the income approach to value our debt investments similar to the approaches used for our control LMM portfolio investments, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. Our estimate of the expected repayment date of a LMM debt security is generally the legal maturity date of the instrument, as we generally intend to hold our LMM loans and debt securities to maturity. The yield-to-maturity analysis considers changes in leverage levels, credit quality, portfolio company performance and other factors. We will use the value determined by the yield-to-maturity analysis as the fair value for that security; however, because of our general intent to hold our loans to maturity, the fair value will not exceed the face amount of the LMM debt security. A

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change in the assumptions that we use to estimate the fair value of our LMM debt securities using the yield-to-maturity analysis could have a material impact on the determination of fair value. If there is deterioration in credit quality or if a LMM debt security is in workout status, we may consider other factors in determining the fair value of the LMM debt security, including the value attributable to the debt security from the enterprise value of the portfolio company or the proceeds that would most likely be received in a liquidation analysis.

        Our Middle Market portfolio investments primarily consist of direct or secondary investments in interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our Investment Portfolio. For valuation purposes, all of our Middle Market portfolio investments are non-control investments for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. We primarily use observable inputs to determine the fair value of these investments through obtaining third party quotes or independent pricing, to the extent such sufficient observable inputs are available to determine fair value. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        Our Private Loan portfolio investments primarily consist of direct or secondary investments in interest-bearing debt securities in companies that are consistent with the size of companies included in our LMM portfolio or our Middle Market portfolio. For valuation purposes, all of Main Street's Private Loan portfolio investments are non-control investments for which Main Street does not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. As sufficient observable inputs to determine the fair value of these Private Loan portfolio investments through obtaining third party pricing or other independent pricing are not generally available, Main Street generally uses a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value its LMM portfolio debt investments.

        For valuation purposes, all of our Other Portfolio investments are non-control investments for which we generally do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Main Street's Other Portfolio investments comprised 2.9% and 2.6%, respectively, of Main Street's Investment Portfolio at fair value as of March 31, 2013 and December 31, 2012. Similar to the LMM investment portfolio, market quotations for Other Portfolio equity investments are generally not readily available. For our Other Portfolio equity investments, we determine the fair value based on the fair value of the portfolio company as determined by independent third parties and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. For Other Portfolio debt investments with observable inputs, we determine the fair value of these investments through obtaining third party quotes or other independent pricing, to the extent such sufficient observable inputs are available to determine fair value. To the extent observable inputs are not available, we value these Other Portfolio debt investments through an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        Due to the inherent uncertainty in the valuation process, our determination of fair value for our Investment Portfolio may differ materially from the values that would have been used had a ready market for the securities existed. In addition, changes in the market environment, portfolio company performance and other events that may occur over the lives of the investments may cause the gains or losses ultimately realized on these investments to be materially different than the valuations currently assigned. We determine the fair value of each individual investment and record changes in fair value as unrealized appreciation or depreciation.

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Revenue Recognition

Interest and Dividend Income

        We record interest and dividend income on the accrual basis to the extent amounts are expected to be collected. Dividend income is recorded as dividends are declared or at the point an obligation exists for the portfolio company to make a distribution. In accordance with our valuation policy, we evaluate accrued interest and dividend income periodically for collectability. When a loan or debt security becomes 90 days or more past due, and if we otherwise do not expect the debtor to be able to service all of its debt or other obligations, we will generally place the loan or debt security on non-accrual status and cease recognizing interest income on that loan or debt security until the borrower has demonstrated the ability and intent to pay contractual amounts due. If a loan or debt security's status significantly improves regarding the debtor's ability to service the debt or other obligations, or if a loan or debt security is fully impaired, sold or written off, we will remove it from non-accrual status.

Fee Income

        We may periodically provide services, including structuring and advisory services, to our portfolio companies. For services that are separately identifiable and evidence exists to substantiate fair value, income is recognized as earned, which is generally when the investment or other applicable transaction closes. Fees received in connection with debt financing transactions for services that do not meet these criteria are treated as debt origination fees and are deferred and accreted into interest income over the life of the financing.

Payment-in-Kind ("PIK") Interest and Cumulative Dividends

        We hold debt and preferred equity instruments in our Investment Portfolio that contain payment-in-kind ("PIK") interest and cumulative dividend provisions. The PIK interest, computed at the contractual rate specified in each debt agreement, is periodically added to the principal balance of the debt and is recorded as interest income. Thus, the actual collection of this interest may be deferred until the time of debt principal repayment. Cumulative dividends are recorded as dividend income, and any unpaid dividends are added to the balance of the preferred equity investment. The actual collection of these dividends in arrears may be deferred until such time as the preferred equity is redeemed. To maintain RIC tax treatment (as discussed below), these non-cash sources of income may need to be paid out to stockholders in the form of distributions, even though we may not have collected the PIK interest and cumulative dividends in cash. We will stop accruing PIK interest and cumulative dividends and will write off any accrued and uncollected interest and dividends in arrears when it is determined that such PIK interest and dividends in arrears are no longer collectible.

Share-Based Compensation

        We account for our share-based compensation plans using the fair value method, as prescribed by ASC 718, Compensation—Stock Compensation. Accordingly, for restricted stock awards, we measured the grant date fair value based upon the market price of our common stock on the date of the grant and will amortize this fair value to share-based compensation expense over the requisite service period or vesting term.

Income Taxes

        MSCC has elected to be treated for federal income tax purposes as a RIC. As a RIC, MSCC generally will not pay corporate-level federal income taxes on any net ordinary income or capital gains that MSCC distributes to its stockholders as dividends. MSCC must generally distribute at least 90% of its investment company taxable income to qualify for pass-through tax treatment and maintain its RIC status. As part of maintaining RIC status, undistributed taxable income (subject to a 4% excise tax)

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pertaining to a given fiscal year may be distributed up to 12 months subsequent to the end of that fiscal year, provided such dividends are declared prior to the filing of the federal income tax return for the prior year.

        The Taxable Subsidiaries hold certain portfolio investments for us. The Taxable Subsidiaries are consolidated with us for financial reporting purposes, and the portfolio investments held by the Taxable Subsidiaries are included in Main Street's consolidated financial statements. The principal purpose of the Taxable Subsidiaries is to permit Main Street to hold equity investments in portfolio companies which are "pass through" entities for tax purposes in order to comply with the "source income" requirements contained in the RIC tax provisions of the Code. The Taxable Subsidiaries are not consolidated with Main Street for income tax purposes and may generate income tax expense or income tax benefit as a result of their ownership of various portfolio investments. This income tax expense or benefit, if any, is reflected in our Consolidated Statement of Operations.

        The Taxable Subsidiaries use the liability method in accounting for income taxes. Deferred tax assets and liabilities are recorded for temporary differences between the tax basis of assets and liabilities and their reported amounts in the financial statements, using statutory tax rates in effect for the year in which the temporary differences are expected to reverse. A valuation allowance is provided against deferred tax assets when it is more likely than not that some portion or all of the deferred tax asset will not be realized.

        Taxable income generally differs from net income for financial reporting purposes due to temporary and permanent differences in the recognition of income and expenses. Taxable income generally excludes net unrealized appreciation or depreciation, as investment gains or losses are not included in taxable income until they are realized.

INVESTMENT PORTFOLIO COMPOSITION

        LMM portfolio investments principally consist of secured debt, equity warrants and direct equity investments in privately held, LMM companies. The LMM debt investments are primarily secured by either a first or second lien on the assets of the portfolio company, generally bear interest at fixed rates, and generally mature between five and seven years from the original investment date. In most LMM portfolio companies, we also receive nominally priced equity warrants and/or make direct equity investments, usually in connection with a debt investment.

        Middle Market portfolio investments primarily consist of direct or secondary investments in interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien and typically have a term of between three and five years.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of companies included in our LMM portfolio or our Middle Market portfolio. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have a term of between three and seven years.

        Our Other Portfolio investments primarily consist of investments which are not consistent with the typical profiles for LMM, Middle Market and Private Loan portfolio investments, including investments which may be managed by third parties. In the Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds. As of March 31, 2013, we had Other Portfolio investments in 4 companies, collectively totaling approximately $28.7 million in fair value and approximately $27.9 million in cost basis and which comprised 2.9% of our Investment Portfolio at fair value as of March 31, 2013.

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        The following tables summarize the composition of our total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments at cost and fair value by type of investment as a percentage of the total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments as of March 31, 2013 and December 31, 2012 (this information excludes the Other Portfolio investments and the Investment Manager).

 

        The following tables summarize the composition of the total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments by geographic region of the United States or other countries at cost and fair value as a percentage of the total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments, as of March 31, 2013 and December 31, 2012 (this information excludes the Other Portfolio investments and the Investment Manager). The geographic composition is determined by the location of the corporate headquarters of the portfolio company.

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        Our LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments are in companies conducting business in a variety of industries. The following tables summarize the composition of our total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments, by industry at cost and fair value as of March 31, 2013 and December 31, 2012 (this information excludes the Other Portfolio investments and the Investment Manager).

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        Our LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments carry a number of risks including, but not limited to: (1) investing in LMM, Middle Market, Private Loan and Other Portfolio companies which may have limited operating histories and financial resources; (2) holding investments that generally are not publicly traded and which may be subject to legal and other restrictions on resale; and (3) other risks common to investing in below investment grade debt and equity investments in our Investment Portfolio.

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PORTFOLIO ASSET QUALITY

        We utilize an internally developed investment rating system to rate the performance of each LMM portfolio company and to monitor our expected level of returns on each of our LMM investments in relation to our expectations for the portfolio company. The investment rating system takes into consideration various factors, including but not limited to each investment's expected level of returns and the collectability of our debt investments, comparisons to competitors and other industry participants and the portfolio company's future outlook. Investment Rating 1 represents a LMM portfolio company that is performing in a manner which significantly exceeds expectations. Investment Rating 2 represents a LMM portfolio company that, in general, is performing above expectations. Investment Rating 3 represents a LMM portfolio company that is generally performing in accordance with expectations. Investment Rating 4 represents a LMM portfolio company that is underperforming expectations. Investments with such a rating require increased monitoring and scrutiny by us. Investment Rating 5 represents a LMM portfolio company that is significantly underperforming. Investments with such a rating require heightened levels of monitoring and scrutiny by us and involve the recognition of significant unrealized depreciation on such investment. All new LMM portfolio investments receive an initial Investment Rating of 3.

        The following table shows the distribution of our LMM portfolio investments on the 1 to 5 investment rating scale at fair value as of March 31, 2013 and December 31, 2012:

        Based upon our investment rating system, the weighted average rating of our LMM portfolio was approximately 2.2 as of March 31, 2013 and 2.1 as of December 31, 2012.

        For the total Investment Portfolio, as of March 31, 2013, we had one investment with positive fair value on non-accrual status which comprised 0.2% of the total Investment Portfolio at fair value and, together with another fully impaired investment, comprised approximately 0.7% of the total Investment Portfolio at cost, excluding the investment in the affiliated Investment Manager. As of December 31, 2012, we had no investments with positive fair value on non-accrual status and one fully impaired investment which comprised approximately 0.2% of the total Investment Portfolio at cost, excluding the investment in the affiliated Investment Manager.

        The broader fundamentals of the United States economy remain mixed, and unemployment remains elevated. In the event that the United States economy contracts, it is likely that the financial results of small- to mid-sized companies, like those in which we invest, could experience deterioration or limited growth from current levels, which could ultimately lead to difficulty in meeting their debt service requirements and an increase in defaults. Consequently, we can provide no assurance that the performance of certain portfolio companies will not be negatively impacted by economic cycles or other conditions, which could also have a negative impact on our future results.

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DISCUSSION AND ANALYSIS OF RESULTS OF OPERATIONS

Comparison of the three months ended March 31, 2013 and March 31, 2012

 

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Investment Income

        For the three months ended March 31, 2013, total investment income was $25.6 million, a 25% increase over the $20.6 million of total investment income for the corresponding period of 2012. This comparable period increase was principally attributable to (i) a $3.6 million increase in interest income from higher average levels of portfolio debt investments and increased activity in the Investment Portfolio, (ii) a $1.0 million increase in dividend income from portfolio equity investments and (iii) a $0.4 million increase in fee income due to the increased activity in and size of the Investment Portfolio. The $5.0 million increase in investment income in the first quarter of 2013 includes a $1.2 million net decrease in investment income related to accelerated prepayment and repricing activity for certain portfolio debt investments and marketable securities investments when compared to the same period in 2012. This $1.2 million net decrease is due to the inclusion of $1.8 million of non-recurring investment income associated with debt repayment and financing activities in two LMM portfolio investments in investment income in the first three months of 2012 partially offset by an increase in investment income related to higher accelerated prepayment and repricing activity of certain Middle Market portfolio debt investments of $0.6 million in the first quarter of 2013.

Expenses

        For the three months ended March 31, 2013, total expenses increased to $8.3 million from $7.7 million for the corresponding period of 2012. This comparable period increase in operating expenses was principally attributable to higher compensation and related expenses of $0.4 million primarily as a result of additional personnel and a $0.2 million increase in other general and administrative expenses compared to the corresponding period of 2012. The ratio of our total operating expenses, excluding interest expense, as a percentage of our average total assets was 1.7% on an annualized basis for the three months ended March 31, 2013, compared to 2.0% for the comparable period in the prior year.

Distributable Net Investment Income

        Distributable net investment income increased 33% to $17.9 million, or $0.52 per share, compared with $13.4 million, or $0.50 per share, in the corresponding period of 2012. The increase in distributable net investment income was primarily due to the higher level of total investment income partially offset by higher operating expenses, due to the changes discussed above. Distributable net investment income on a per share basis for the three months ended March 2013 reflects (i) a decrease of approximately $0.06 per share from the comparable period in 2012 attributable to certain non-recurring items in such prior period and the comparable levels of accelerated prepayment and repricing activity for certain debt investments and marketable securities investments as discussed above and (ii) a greater number of average shares outstanding compared to the corresponding period in 2012 primarily due to the June 2012 and December 2012 follow-on stock offerings.

Net Investment Income

        Net investment income for the three months ended March 31, 2013 was $17.3 million, or a 35% increase, compared to net investment income of $12.9 million for the corresponding period of 2012. The increase in net investment income was principally attributable to the increase in total investment income partially offset by higher operating expenses as discussed above.

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Distributable Net Realized Income

        Distributable net realized income was $17.5 million, or $0.50 per share, for the three months ended 2013 compared with distributable net realized income of $21.6 million, or $0.80 per share, in the corresponding period of 2012. The $4.1 million decrease was primarily attributable to the decrease in net realized gain from investments of $8.6 million, partially offset by higher distributable net investment income in the three months ended March 31, 2013 compared to the corresponding period of 2012 as discussed above. The $8.2 million net realized gain from investments during the first quarter of 2012 was primarily attributable to (i) realized gains totaling $11.9 million recognized on the full or partial exits of equity investments in two LMM portfolio companies and net realized gains related to Middle Market debt and marketable securities investments, partially offset by (ii) realized losses totaling $3.8 million on the full exits of investments in two LMM portfolio companies.

Net Realized Income

        The lower level of net realized gain from investments, partially offset by higher net investment income in the three months ended March 31, 2013 compared to the corresponding period of 2012, both as discussed above, resulted in a $4.2 million decrease in net realized income compared with the corresponding period of 2012.

Net Increase in Net Assets Resulting from Operations Attributable to Common Stock

        The net increase in net assets resulting from operations attributable to common stock during the three months ended March 31, 2013 was $23.6 million, or $0.68 per share, compared with a net increase of $23.8 million, or $0.89 per share, in the first quarter of 2012. This $0.2 million decrease from the comparable period in the prior year was primarily the result of the decrease in net realized income as discussed above, partially offset by $4.1 million increase in the net change in unrealized appreciation to $8.8 million in the first quarter of 2013, compared to $4.7 million for the comparable period in the prior year. The total net change in unrealized appreciation for the first quarter of 2013 of $8.8 million included a $10.0 million net change in unrealized appreciation from portfolio investments, partially offset by the net change in unrealized depreciation of $1.2 million on the SBIC debentures held by MSC II. The $10.0 million net change in unrealized appreciation from portfolio investments for the three months ended March 31, 2013 was principally attributable to (i) unrealized appreciation on 17 LMM portfolio investments totaling $10.3 million, partially offset by unrealized depreciation on 10 LMM portfolio investments totaling $4.3 million and (ii) $4.7 million of net unrealized appreciation on the Middle Market investment portfolio, partially offset by (iii) accounting reversals of net unrealized appreciation from prior periods of $1.4 million related to portfolio investment exits and repayments. For the three months ended March 31, 2013, we also recognized a net income tax provision of $2.1 million related to deferred taxes of $1.4 million and other taxes of $0.7 million. The deferred taxes related primarily to net unrealized appreciation on equity investments held in our taxable subsidiaries. The other taxes include $0.4 million related to an accrual for excise tax on our estimated spillover taxable income and $0.3 million related to accruals for state and other taxes.

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Comparison of years ended December 31, 2012 and December 31, 2011

 

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Investment Income

        For the year ended December 31, 2012, total investment income was $90.5 million, a $24.3 million, or 37%, increase over the $66.2 million for the corresponding period of 2011. This comparable period increase was principally attributable to (i) a $19.1 million increase in interest income from increased activity in the investment portfolio and higher average levels of portfolio debt investments and interest-bearing marketable securities investments, (ii) a $3.2 million increase in dividend income from portfolio equity investments and (iii) a $2.0 million increase in fee income due to the increased activity in and size of the investment portfolio. The increase in investment income included (i) $1.8 million of non-recurring investment income during the first quarter of 2012 associated with repayment and financing activities for two LMM portfolio investments, (ii) a $3.2 million increase in investment income associated with higher levels of accelerated prepayment activity for certain Middle Market portfolio debt investments and marketable securities investments in comparison to 2011 and (iii) special dividend activity of $1.4 million in the fourth quarter of 2012.

Expenses

        For the year ended December 31, 2012, total expenses increased by approximately $4.3 million, or 16%, to $31.2 million from $26.9 million for the corresponding period of 2011. This comparable period increase in expenses was principally attributable to (i) higher interest expense of $2.1 million as a result of the net issuance of an additional $5 million in SBIC debentures subsequent to December 31, 2011, increased borrowing activity under the Credit Facility and higher unused fees associated with the increased commitments under the Credit Facility, (ii) higher share-based compensation expense of $0.5 million related to non-cash amortization for restricted share grants, and (iii) higher compensation and expenses of $1.7 million related to increases in personnel and incentive compensation compared to the corresponding period of 2011. For the years ended December 31, 2012 and 2011, the ratio of our total operating expenses, excluding interest expense, as a percentage of our quarterly average total assets was 1.8% and 2.2%, respectively.

Distributable Net Investment Income

        Distributable net investment income for the year ended December 31, 2012 increased to $61.9 million, or $2.09 per share, compared with distributable net investment income of $41.3 million, or $1.77 per share, for the corresponding period of 2011. The increase in distributable net investment income was primarily due to the higher level of total investment income partially offset by higher interest and other operating expenses, due to the changes discussed above. Distributable net investment income on a per share basis for the year ended 2012 reflects (i) an increase of approximately $0.13 per share from 2011 in investment income attributable to higher levels of accelerated prepayment and repricing activity for certain debt investments and marketable securities investments, (ii) approximately $0.05 per share from the special dividend activity in the fourth quarter of 2012 and (iii) a greater number of average shares outstanding compared to the corresponding period in 2011 primarily due to the net effect of December 2012, June 2012, October 2011 and March 2011 follow-on stock offerings.

Net Investment Income

        Net investment income for the year ended December 31, 2012 was $59.3 million, or a 51% increase, compared to net investment income of $39.3 million for the corresponding period of 2011. The increase in net investment income was principally attributable to the increase in total investment income partially offset by higher interest and other operating expenses as discussed above.

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Distributable Net Realized Income

        Distributable net realized income increased to $78.4 million, or $2.65 per share, for the year ended 2012 compared with distributable net realized income of $44.0 million, or $1.89 per share, for the corresponding period of 2011. The increase was primarily attributable to the higher level of distributable net investment income and the higher level of total net realized gain from investments in 2012 compared to the corresponding period of 2011. The $16.5 million net realized gain during 2012 was primarily attributable to (i) realized gains recognized on two partial exits of LMM portfolio company equity investments, (ii) a realized gain recognized on the full exit of a LMM portfolio company equity investment and (iii) realized gains related to Middle Market and marketable securities investments, partially offset by (iv) realized losses on the full exits of three LMM portfolio company investments.

Net Realized Income

        The higher level of net investment income and the higher level of total net realized gain from investments in 2012 compared to the corresponding period of 2011, both as discussed above, resulted in a $33.8 million increase in net realized income compared with the corresponding period of 2011.

Net Increase in Net Assets Resulting from Operations

        The net increase in net assets resulting from operations attributable to common stock during the year ended December 31, 2012 was $104.4 million, or $3.53 per share, compared with a net increase of $63.0 million, or $2.76 per share, in 2011. This $41.4 million increase was a result of the increase in net realized income discussed above, plus differences in the net change in unrealized appreciation from portfolio investments, marketable securities, SBIC debentures and investment in the Investment Manager and the difference in the income tax provision. For the year ended December 31, 2012, the $44.5 million net change in unrealized appreciation from portfolio investments was principally attributable to (i) unrealized appreciation on 37 LMM portfolio investments totaling $57.8 million, partially offset by unrealized depreciation on 10 LMM portfolio investments totaling $4.6 million, (ii) $9.7 million of net unrealized appreciation on the Middle Market investment portfolio and (iii) $0.8 million of net unrealized appreciation on the Other Portfolio investments and Marketable securities and idle funds investments, partially offset by (iv) accounting reversals of net unrealized appreciation from prior periods of $18.3 million related to portfolio investment exits and repayments, and (v) accounting reversals of net unrealized appreciation from prior periods of $0.5 million related to Marketable securities and idle funds investments exits and repayments. For the year ended December 31, 2012, the $5.0 million net change in unrealized appreciation attributable to SBIC debentures and investment in the Investment Manager was primarily attributable to unrealized depreciation on the SBIC debentures held by MSC II. The noncontrolling interest of $0.1 million recognized during the first quarter of 2012 reflects the pro rata portion of the net increase in net assets resulting from operations for MSC II attributable to the equity interests in MSC II that were not owned by MSCC prior to MSCC's completion of the Final MSC II Exchange. For the year ended December 31, 2012, we also recognized a net income tax provision of $10.8 million related to deferred taxes of $8.0 million and other taxes of $2.8 million. The deferred taxes related primarily to net unrealized appreciation on equity investments held in our taxable subsidiaries. The other taxes include $1.6 million related to an accrual for excise tax on our estimated spillover taxable income as of December 31, 2012 and $1.2 million related to accruals for state and other taxes.

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Comparison of years ended December 31, 2011 and December 31, 2010

 

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Investment Income

        For the year ended December 31, 2011, total investment income was $66.2 million, a $29.7 million, or 81%, increase over the $36.5 million of total investment income for the corresponding period of 2010. This comparable period increase was principally attributable to (i) a $23.8 million increase in interest income from higher average levels of both portfolio debt investments and interest-bearing marketable securities investments, (ii) a $4.3 million increase in dividend income from portfolio equity investments, and (iii) a $1.6 million increase in fee income due to higher levels of transaction activity. The increase in investment income included a $2.7 million increase in investment income associated with higher levels of accelerated prepayment and repricing activity for certain debt investments.

Expenses

        For the year ended December 31, 2011, total expenses increased by approximately $9.7 million, or 56%, to $26.9 million from $17.2 million for the corresponding period of 2010. This comparable period increase in expenses was principally attributable to (i) higher interest expense of $4.5 million as a result of the issuance of an additional $40 million in SBIC debentures subsequent to December 31, 2010, and increased borrowing activity under the Credit Facility, (ii) higher share-based compensation expense of $0.6 million related to non-cash amortization for restricted share grants, and (iii) higher compensation and other operating expenses of $4.7 million related to the significant increase in investment income and portfolio investments compared to the corresponding period of 2010. The ratio of total operating expenses, excluding interest expense, as a percentage of average total assets for the year ended December 31, 2011 was 2.2%, representing an approximate 7% decrease from the same ratio of 2.4% for the year ended December 31, 2010.

Distributable Net Investment Income

        Distributable net investment income for the year ended December 31, 2011 increased to $41.3 million, or $1.77 per share, compared with distributable net investment income of $20.7 million, or $1.25 per share, for the corresponding period of 2010. The increase in distributable net investment income was primarily due to the higher level of total investment income partially offset by higher interest and other operating expenses, due to the changes discussed above. Distributable net investment income on a per share basis for the year ended 2011 reflects approximately $0.12 per share of investment income associated with higher levels of accelerated prepayment and repricing activity for certain debt investments and (ii) a greater number of average shares outstanding compared to the corresponding period in 2010 primarily due to the October 2011, March 2011, and August 2010 follow-on stock offerings.

Net Investment Income

        Net investment income for the year ended December 31, 2011 was $39.3 million, or a 104% increase, compared to net investment income of $19.3 million for the corresponding period of 2010. The increase in net investment income was principally attributable to the increase in total investment income partially offset by higher interest and other operating expenses as discussed above.

Distributable Net Realized Income

        Distributable net realized income increased to $44.0 million, or $1.89 per share, for the year ended 2011 compared with distributable net realized income of $17.8 million, or $1.08 per share, for the corresponding period of 2010. The increase was primarily attributable to the higher level of distributable net investment income as well as the higher level of total net realized gain from investments in 2011 compared to the net realized loss from investments in the corresponding period of 2010. The $2.6 million net realized gain during 2011 was primarily attributable to (i) realized gain

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recognized on one partial exit of an LMM portfolio company equity investment, (ii) realized gain recognized on one full exit of an LMM portfolio company equity investment, and (iii) realized gains related to Middle Market and marketable securities investments. The $2.9 million net realized loss during the 2010 year was primarily attributable to $5.9 million of realized loss from our debt and equity investments in two portfolio companies, partially offset by (i) $2.3 million of realized gain on two partial exits and one full exit of portfolio company equity investments and (ii) $0.7 million of realized gain related to Middle Market and marketable securities and idle funds investments.

Net Realized Income

        The higher level of net investment income and the change from net realized loss to net realized gain from investments during 2011 resulted in a $25.6 million increase in net realized income compared with the corresponding period of 2010.

Net Increase in Net Assets Resulting from Operations

        For the year ended December 31, 2011, the $28.4 million net change in unrealized appreciation was principally attributable to (i) unrealized appreciation on 30 LMM portfolio investments totaling $53.6 million, partially offset by unrealized depreciation on 11 LMM portfolio investments totaling $11.8 million, (ii) $3.7 million of net unrealized depreciation on Middle Market portfolio investments and marketable securities and idle funds investments, (iii) accounting reversals of net unrealized appreciation related to the net realized gains recognized during 2011 in the amounts of $2.8 million for portfolio investments and $0.4 million for marketable securities and idle funds investments, (iv) $6.3 million of net unrealized depreciation attributable to our SBIC debentures, and (v) $0.2 million in unrealized depreciation attributable to our investment in the affiliated Investment Manager. The noncontrolling interest of $1.1 million recognized during 2011 reflects the pro rata portion of MSC II net earnings attributable to the equity interests in MSC II not owned by Main Street. For the year ended December 31, 2011, we also recognized a net income tax provision of $6.3 million principally related to deferred taxes on net unrealized appreciation of certain portfolio investments held in our Taxable Subsidiaries.

        As a result of these events, our net increase in net assets resulting from operations attributable to common stock during 2011 was $63.0 million, or $2.76 per share, compared with a net increase in net assets resulting from operations attributable to common stock of $38.7 million, or $2.38 per share, in 2010.

Liquidity and Capital Resources

Cash Flows

        For the three months ended March 31, 2013, we experienced a net decrease in cash and cash equivalents in the amount of $37.3 million. During the period, we used $24.3 million of cash for our operating activities, primarily from (i) the funding of new portfolio company investments and settlement of accruals for portfolio investments at December 31, 2012, which together total $126.0 million, (ii) the settlement of $16.7 million of accruals for Marketable securities and idle funds investments at December 31, 2012, and (iii) $8.5 million related to decreases in payables and accruals, which such cash uses offset by (i) $81.4 million in cash proceeds from the sales and repayments of debt investments, (ii) $28.8 million of cash proceeds from the sale of Marketable securities and idle funds investments, (iii) distributable net investment income, excluding the non-cash effects of the accretion of unearned income, payment-in-kind interest income and the amortization of deferred financing costs, and (iv) decreases in other assets of $3.3 million. During the three months ended March 31, 2013, $13.0 million in cash was used in financing activities, which principally consisted of $22.4 million in cash

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dividends paid to stockholders, partially offset by $9.0 million in net cash proceeds from our credit facility (the "Credit Facility").

        For the year ended December 31, 2012, we experienced a net increase in cash and cash equivalents in the amount of $20.9 million. During that period, we generated $48.9 million of cash from our operating activities, primarily from (i) distributable net investment income, excluding the non-cash effects of the accretion of unearned income, payment-in-kind interest income and the amortization of deferred financing costs, (ii) increases in payables, and (iii) realized gains, partially offset by increases in interest receivable. We used $184.5 million in net cash from investing activities, principally including the funding of $639.8 million for new portfolio company investments and the funding of $14.4 million for Marketable securities and idle funds investments, partially offset by (i) $400.0 million in cash proceeds from the repayment of portfolio debt investments, (ii) $35.1 million in cash proceeds from the exit of portfolio equity investments and (iii) $34.5 million of cash proceeds from the sale of Marketable securities and idle funds investments. During 2012, $156.5 million in cash was provided by financing activities, which principally consisted of (i) $169.9 million in net cash proceeds from public stock offerings in June and December 2012, (ii) $25.0 million in net cash proceeds from the Credit Facility and (iii) $5.0 million in net cash proceeds from the issuance of SBIC debentures, partially offset by (i) $39.9 million in cash dividends paid to stockholders and (ii) $2.2 million in loan costs associated with our SBIC debentures and the Credit Facility.

        For the year ended December 31, 2011, we experienced a net increase in cash and cash equivalents in the amount of $20.3 million. During that period, we generated $37.2 million of cash from our operating activities, primarily from (i) distributable net investment income, excluding the non-cash effects of the accretion of unearned income, payment-in-kind interest income and the amortization of deferred financing costs, (ii) increases in payables, and (iii) realized gains, partially offset by (iv) increases in interest receivable. We used $220.5 million in net cash from investing activities, principally including (i) the funding of $358.9 million for new portfolio company investments and (ii) the funding of $33.5 million for Marketable securities and idle funds investments, partially offset by (i) $160.2 million in cash proceeds from the repayment of portfolio debt investments and from the exit of portfolio equity investments and (ii) $11.7 million of cash proceeds from the sale of Marketable securities and idle funds investments. During 2011, $203.6 million in cash was provided by financing activities, which principally consisted of (i) $127.8 million in net cash proceeds from public stock offerings in March 2011 and October 2011, (ii) $40.0 million in cash proceeds from the issuance of SBIC debentures, and (iii) $68.0 million in net cash proceeds from the Credit Facility, partially offset by $28.3 million in cash dividends paid to stockholders and $2.3 million in loan costs associated with our SBIC debentures and credit facility.

        For the year ended December 31, 2010, we experienced a net decrease in cash and cash equivalents in the amount of $8.3 million. During that period, we generated $16.6 million of cash from our operating activities, primarily from distributable net investment income partially offset by increases in interest receivable. We used $176.0 million in net cash from investing activities, principally including the funding of $157.7 million for new portfolio company investments and the funding of $100.6 million for Marketable securities and idle funds investments, partially offset by (i) $36.8 million of cash proceeds from the sale of Marketable securities and idle funds investments, (ii) $43.0 million in cash proceeds from the repayment of portfolio debt investments and from the exit of portfolio equity investments, and (iii) $2.5 million in cash acquired as part of the Exchange Offer. During 2010, $151.1 million in cash was provided by financing activities, which principally consisted of (i) $85.9 million in net cash proceeds from public stock offerings in January 2010 and August 2010, (ii) $45.0 million in cash proceeds from the issuance of SBIC debentures, and (iii) $39 million in net cash proceeds from the Credit Facility, partially offset by $16.3 million in cash dividends paid to stockholders and $2.1 million in loan costs associated with our SBIC debentures and the Credit Facility.

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Capital Resources

        As of March 31, 2013, we had $26.2 million in cash and cash equivalents and $146.5 million of unused capacity under the Credit Facility, which we maintain to support our future investment and operating activities. As of March 31, 2013, our net asset value totaled $645.2 million, or $18.55 per share.

        The Credit Facility, as amended, currently provides for $287.5 million in total commitments from a diversified group of nine lenders. The Credit Facility contains an accordion feature which allows Main Street to increase the total commitments under the facility up to $400 million from new or existing lenders on the same terms and conditions as the existing commitments.

        Borrowings under the Credit Facility bear interest, subject to our election, on a per annum basis equal to (i) the applicable LIBOR rate (0.20%, as of March 31, 2013) plus 2.50% or (ii) the applicable base rate (Prime Rate, 3.25% as of March 31, 2013) plus 1.50%. We pay unused commitment fees of 0.375% per annum on the unused lender commitments under the Credit Facility. The Credit Facility is secured by a first lien on the assets of MSCC and its subsidiaries, excluding the assets of the Funds. The Credit Facility contains certain affirmative and negative covenants, including but not limited to: (i) maintaining an interest coverage ratio of at least 2.0 to 1.0, (ii) maintaining an asset coverage ratio of at least 2.5 to 1.0, and (iii) maintaining a minimum tangible net worth. The Credit Facility includes an initial revolving period through September 2015 followed by a two-year term out period with a final maturity in September 2017, and contains two, one-year extension options which could extend both the revolving period and the final maturity by up to two years, subject to certain conditions including lender approval. At March 31, 2013, we had $141 million in borrowings outstanding under the Credit Facility. As of March 31, 2013, the interest rate on the Credit Facility was 2.70%, and Main Street was in compliance with all financial covenants of the Credit Facility.

        In June 2012, we completed a follow-on public stock offering in which we sold 4,312,500 shares of common stock, including the underwriters' full exercise of the over-allotment option, at a price to the public of $22.50 per share (or approximately 143% of the then latest reported Net Asset Value per share), resulting in total net proceeds of approximately $93.0 million, after deducting underwriters' commissions and offering costs. In December 2012, we completed a follow-on public stock offering in which we sold 2,875,000 shares of common stock, including the underwriters' full exercise of the over-allotment option, at a price to the public of $28.00 per share (or approximately 160% of the then latest reported Net Asset Value per share), resulting in total net proceeds of approximately $77.1 million, after deducting underwriters' commissions and offering costs.

        Due to each of the Funds' status as a licensed SBIC, we have the ability to issue, through the Funds, debentures guaranteed by the SBA at favorable interest rates. Under the regulations applicable to SBIC funds, an SBIC can have outstanding debentures guaranteed by the SBA generally in an amount up to twice its regulatory capital, which effectively approximates the amount of its equity capital. Debentures guaranteed by the SBA have fixed interest rates that equal prevailing 10-year Treasury Note rates plus a market spread and have a maturity of ten years with interest payable semi-annually. The principal amount of the debentures is not required to be paid before maturity but may be pre-paid at any time with no prepayment penalty. On March 31, 2013, we, through the Funds, had $225 million of outstanding indebtedness guaranteed by the SBA, which carried a weighted average annual fixed interest rate of approximately 4.8%. The first maturity related to the SBIC debentures does not occur until 2014, and the remaining weighted average duration is approximately 6.1 years as of March 31, 2013.

        We anticipate that we will continue to fund our investment activities through existing cash and cash equivalents and a combination of future debt and equity capital. Our primary uses of funds will be investments in portfolio companies, operating expenses and cash distributions to holders of our common stock.

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        We periodically invest excess cash balances into Marketable securities and idle funds investments. The primary investment objective of Marketable securities and idle funds investments is to generate incremental cash returns on excess cash balances prior to utilizing those funds for investment in our LMM, Middle Market and Private Loan portfolio investment strategy. Marketable securities and idle funds investments generally consist of debt investments, independently rated debt investments, certificates of deposit with financial institutions, and diversified bond funds. The composition of Marketable securities and idle funds investments will vary in a given period based upon, among other things, changes in market conditions, the underlying fundamentals in our Marketable securities and idle funds investments, our outlook regarding future LMM, Middle Market and Private Loan portfolio investment needs, and any regulatory requirements applicable to Main Street.

        If our common stock trades below our net asset value per share, we will generally not be able to issue additional common stock at the market price unless our stockholders approve such a sale and our Board of Directors makes certain determinations. A proposal, approved by our stockholders at our June 2012 annual meeting of stockholders, authorizes us to sell shares of our common stock below the then current net asset value per share of our common stock in one or more offerings for the period ending on June 13, 2013, the date of our 2013 annual meeting of stockholders. We would need similar future approval from our stockholders to issue shares below the then current net asset value per share any time after the expiration of the current approval. We are not currently seeking such approval at our 2013 annual meeting of stockholders because our common stock price per share has been trading significantly above the current net asset value per share of our common stock.

        In order to satisfy the Code requirements applicable to a RIC, we intend to distribute to our stockholders substantially all of our taxable income, but we may also elect to periodically spillover certain excess undistributed taxable income from one tax year into the next tax year. In addition, as a BDC, we generally are required to meet a coverage ratio of total assets to total senior securities, which include borrowings and any preferred stock we may issue in the future, of at least 200%. This requirement limits the amount that we may borrow. In January 2008, we received an exemptive order from the SEC to exclude SBA-guaranteed debt securities issued by MSMF and any other wholly owned subsidiaries of ours which operate as SBICs from the asset coverage requirements of the 1940 Act as applicable to Main Street, which, in turn, enables us to fund more investments with debt capital.

        Although we have been able to secure access to additional liquidity, including recent public stock offerings, our expanded $287.5 million Credit Facility, and the available leverage through the SBIC program, there is no assurance that debt or equity capital will be available to us in the future on favorable terms, or at all.

Recently Issued Accounting Standards

        From time to time, new accounting pronouncements are issued by the FASB or other standards setting bodies that are adopted by us as of the specified effective date. We believe that the impact of recently issued standards that are not yet effective will not have a material impact on our financial statements upon effectiveness.

Inflation

        Inflation has not had a significant effect on our results of operations in any of the reporting periods presented herein. However, our portfolio companies have experienced, and may in the future experience, the impacts of inflation on their operating results, including periodic escalations in their costs for raw materials and required energy consumption.

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Off-Balance Sheet Arrangements

        We may be a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financial needs of our portfolio companies. These instruments include commitments to extend credit and involve, to varying degrees, elements of liquidity and credit risk in excess of the amount recognized in the balance sheet. At March 31, 2013, we had a total of $100.5 million in outstanding commitments comprised of (i) eight commitments to fund revolving loans that had not been fully drawn and (ii) six capital commitments that had not been fully called.

Contractual Obligations

        As of March 31, 2013, the future fixed commitments for cash payments in connection with our SBIC debentures for each of the next five years and thereafter are as follows:

        As of March 31, 2013, we had $141.0 million in borrowings outstanding under our Credit Facility and the Credit Facility is currently scheduled to mature in September 2017. The Credit Facility contains two, one year extension options which could extend the maturity to September 2019. See further discussion of the Credit Facility terms in "—Liquidity and Capital Resources—Capital Resources."

        Pursuant to the support services agreement with MSCC, the Investment Manager is reimbursed each quarter by MSCC for its cash operating expenses, less fees that the Investment Manager receives from MSC II and third parties, associated with providing investment management and other services to MSCC, certain of its subsidiaries and third parties. For the three months ended March 31, 2013 and 2012, the expenses reimbursed by MSCC to the Investment Manager and management fees paid by MSC II were $3.2 million and $2.7 million, respectively.

Related Party Transactions

        As discussed further in Note D to the accompanying consolidated financial statements, subsequent to the completion of the Formation Transactions, the Investment Manager is a wholly owned portfolio company of MSCC. At March 31, 2013, the Investment Manager had a receivable of $0.1 million due from MSCC related to operating expenses incurred by the Investment Manager required to support Main Street's business.

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SENIOR SECURITIES

        Information about our senior securities is shown in the following table as of December 31 for the years indicated in the table, unless otherwise noted. Grant Thornton LLP's report on the senior securities table as of December 31, 2012, is an exhibit to the registration statement of which this prospectus is a part.

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BUSINESS

        We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies and debt capital to middle market ("Middle Market") companies. Our portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies that operate in diverse industry sectors. We seek to partner with entrepreneurs, business owners and management teams and generally provide "one stop" financing alternatives within our LMM portfolio. We invest primarily in secured debt investments, equity investments, warrants and other securities of LMM companies based in the United States and in secured debt investments of Middle Market companies generally headquartered in the United States. Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million.

        Our private loan ("Private Loan") investments are made in businesses that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. The structure, terms and conditions for these Private Loan investments are typically consistent with the structure, terms and conditions for the loans made in our LMM portfolio or Middle Market portfolio.

        Our other portfolio ("Other Portfolio") investments primarily consist of investments which are not consistent with the typical profiles for our LMM, Middle Market or Private Loan portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

        We seek to fill the current financing gap for LMM businesses, which, historically, have had more limited access to financing from commercial banks and other traditional sources. The underserved nature of the LMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a company's capital structure, from senior secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing options, or a "one stop" financing solution. Providing customized, "one stop" financing solutions has become even more relevant to our LMM portfolio companies in the current investing environment. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our investments. Our LMM portfolio debt investments are generally secured by a first lien on the assets of the portfolio company and typically have a term of between five and seven years. We believe that our LMM investment strategy has a lower correlation to the broader debt and equity markets.

        As of March 31, 2013, we had debt and equity investments in 57 LMM portfolio companies with an aggregate fair value of approximately $520.3 million, with a total cost basis of approximately $412.2 million, and a weighted average annual effective yield on our LMM debt investments of approximately 14.2%. As of March 31, 2013 approximately 76% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 93% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At March 31, 2013, we had equity ownership in approximately 93% of our LMM portfolio companies and the average fully diluted equity

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ownership in those portfolio companies was approximately 33%. As of December 31, 2012, Main Street had debt and equity investments in 56 LMM portfolio companies with an aggregate fair value of approximately $482.9 million, with a total cost basis of approximately $380.5 million, and a weighted average annual effective yield on our LMM debt investments of approximately 14.3%. As of December 31, 2012, approximately 75% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 93.0% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2012, we had equity ownership in approximately 93% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 33%. The weighted average annual yields were computed using the effective interest rates for all debt investments at March 31, 2013 and December 31, 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt instruments and any debt investments on non-accrual status.

        We also pursue investments in Middle Market companies. Our Middle Market portfolio investments primarily consist of direct or secondary purchases of interest-bearing debt securities in privately held companies that are generally larger in size than the LMM companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the company and have an expected duration of between three and five years.

        As of March 31, 2013, we had Middle Market portfolio investments in 80 companies, collectively totaling approximately $361.9 million in fair value with a total cost basis of approximately $354.4 million. The weighted average revenue for the 80 Middle Market portfolio company investments was approximately $557.0 million as of March 31, 2013. As of March 31, 2013, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 91% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 8.2% as of March 31, 2013. As of December 31, 2012, we had Middle Market portfolio investments in 79 companies, collectively totaling approximately $352.0 million in fair value with a total cost basis of approximately $348.1 million. The weighted average revenue for the 79 Middle Market portfolio company investments was approximately $533.6 million as of December 31, 2012. As of December 31, 2012, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 91% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 8.0% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at March 31, 2013 and December 31, 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt instruments.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of the companies included in our LMM portfolio or our Middle Market portfolio. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have a term of between three and seven years.

        As of March 31, 2013, we had Private Loan portfolio investments in 10 companies, collectively totaling approximately $74.5 million in fair value with a total cost basis of approximately $73.8 million. The weighted average revenue for the 10 Private Loan portfolio company investments was approximately $193.8 million as of March 31, 2013. As of March 31, 2013, 99% of our Private Loan portfolio investments were in the form of debt investments and all such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 14.0% as of March 31, 2013. As of

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December 31, 2012, we had Private Loan portfolio investments in 9 companies, collectively totaling approximately $65.5 million in fair value with a total cost basis of approximately $64.9 million. The weighted average revenue for the 9 Private Loan portfolio company investments was approximately $230.5 million as of March 31, 2013. As of December 31, 2012, 99% of our Private Loan portfolio investments were in the form of debt investments and all such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 14.8% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at March 31, 2013 and December 31, 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt instruments.

        As of March 31, 2013, we had Other Portfolio investments in 4 companies, collectively totaling approximately $28.7 million in fair value and approximately $27.9 million in cost basis and which comprised 2.9% of our Investment Portfolio at fair value as of March 31, 2013. As of December 31, 2012, we had Other Portfolio investments in 3 companies, collectively totaling approximately $24.1 million in both fair value and approximately $23.6 million in cost basis and which comprised 2.6% of our Investment Portfolio at fair value as of December 31, 2012.

        During the three months ended March 31, 2013, there were nine portfolio company investment transfers from the LMM and Middle Market portfolio investment categories to the Private Loan portfolio investment category totaling $65.5 million at fair value and $64.9 million at cost as of December 31, 2012.

        Our portfolio investments are generally made through MSCC and the Funds. MSCC and the Funds share the same investment strategies and criteria, although they are subject to different regulatory regimes. An investor's return in MSCC will depend, in part, on the Funds' investment returns as MSMF and MSC II are both wholly owned subsidiaries of MSCC.

        The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria, and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long-term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation will also fluctuate depending upon portfolio activity and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results.

        MSCC and its consolidated subsidiaries are internally managed by the Investment Manager, a wholly owned subsidiary of MSCC, which employs all of the executive officers and other employees of Main Street. Because the Investment Manager is wholly owned by MSCC, Main Street does not pay any external investment advisory fees, but instead incurs the operating costs associated with employing investment and portfolio management professionals through the Investment Manager. We believe that our internally managed structure provides us with a beneficial operating expense structure when compared to other publicly-traded and privately-held investment firms which are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our Investment Portfolio. For the three months ended March 31, 2013 and 2012, the ratio of our total operating expenses, excluding interest expense, as a percentage of our quarterly

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average total assets was 1.7% and 2.0%, respectively, on an annualized basis, and 1.8% for the year ended December 31, 2012.

        During May 2012, MSCC and the Investment Manager executed an investment sub-advisory agreement with HMS Adviser, LP ("HMS Adviser"), which is the investment advisor to HMS Income Fund, Inc. ("HMS Income"), a non publicly-traded BDC whose registration statement on Form N-2 was declared effective by the SEC in June 2012, to provide certain investment advisory services to HMS Adviser. MSCC is initially providing such investment advisory services to HMS Adviser, but it is ultimately intended that the Investment Manager will provide such services because the fees MSCC receives from such arrangement could otherwise have negative consequences on its ability to meet the source-of-income requirement necessary for it to maintain its RIC tax treatment (MSCC or the Investment Adviser, whichever is providing such investment advisory services, the "Sub-Adviser"). Certain relief must be obtained from the SEC before the Investment Manager is permitted to provide these services to HMS Adviser, which relief is being sought, but there can be no assurance that it will be obtained. Under the investment sub-advisory agreement, the Sub-Adviser is entitled to 50% of the base management fee and the incentive fees earned by HMS Adviser under its advisory agreement with HMS Income. However, the Sub-Adviser has agreed to waive all such fees from the effective date of HMS Adviser's registration statement on Form N-2 through September 30, 2013 to the extent that such fees would cause a portion of any distributions declared and payable by HMS Income to represent a return of capital for purposes of U.S. federal income tax. As a result, as of March 31, 2013, the Sub-Adviser has not received any base management fee or incentive fees under the investment sub-advisory agreement and the Sub-Adviser is not due any unpaid compensation for any base management fee or incentive fees under the investment sub-advisory agreement.

Business Strategies

        Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and realizing capital appreciation from our equity and equity-related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. We have adopted the following business strategies to achieve our investment objective:

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Deliver Customized Financing Solutions in the Lower Middle Market.  We believe our ability to provide a broad range of customized financing solutions to LMM companies sets us apart from other capital providers that focus on providing a limited number of financing solutions. We offer to our LMM portfolio companies customized debt financing solutions with equity components that are tailored to the facts and circumstances of each situation. Our ability to invest across a company's capital structure, from senior secured loans to subordinated debt to equity securities, allows us to offer our LMM portfolio companies a comprehensive suite of financing options, or a "one-stop" financing solution.



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Focus on Established Companies.  We generally invest in companies with established market positions, experienced management teams and proven revenue streams. Those companies generally possess better risk-adjusted return profiles than newer companies that are building their management teams or are in the early stages of building a revenue base. We also believe that established companies in our targeted size range also generally provide opportunities for capital appreciation.



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Leverage the Skills and Experience of Our Investment Team.  Our investment team has significant experience in lending to and investing in LMM and Middle Market companies. The members of our investment team have broad investment backgrounds, with prior experience at private investment funds, investment banks and other financial services companies, and currently include six certified public accountants and four Chartered Financial Analyst® (CFA) charter holders.

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The expertise of our investment team in analyzing, valuing, structuring, negotiating and closing transactions should provide us with competitive advantages by allowing us to consider customized financing solutions and non-traditional or complex structures for our portfolio companies. Also, the reputation of our investment team has and should continue to enable us to generate additional revenue in the form of management and incentive fees in connection with us providing advisory services to other investment funds.

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Invest Across Multiple Companies, Industries, Regions and End Markets.  We seek to maintain a portfolio of investments that is appropriately balanced among various companies, industries, geographic regions and end markets. This portfolio balance is intended to mitigate the potential effects of negative economic events for particular companies, regions, industries and end markets.



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Capitalize on Strong Transaction Sourcing Network.  Our investment team seeks to leverage its extensive network of referral sources for portfolio company investments. We have developed a reputation in our marketplace as a responsive, efficient and reliable source of financing, which has created a growing stream of proprietary deal flow for us.



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Benefit from Lower, Fixed, Long-Term Cost of Capital.  The SBIC licenses held by the Funds have allowed them to issue SBA-guaranteed debentures. SBA-guaranteed debentures carry long-term fixed rates that are generally lower than rates on comparable bank and other debt. Because lower cost SBA leverage is, and will continue to be, a significant part of our capital base through the Funds, our relative cost of debt capital should be lower than many of our competitors. In addition, the SBIC leverage that we receive through the Funds represents a stable, long-term component of our capital structure with proper matching of duration and cost compared to our LMM portfolio investments.

Investment Criteria

        Our investment team has identified the following investment criteria that it believes are important in evaluating prospective portfolio companies. Our investment team uses these criteria in evaluating investment opportunities. However, not all of these criteria have been, or will be, met in connection with each of our investments.

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Proven Management Team with Meaningful Equity Stake.  We look for operationally-oriented management with direct industry experience and a successful track record. In addition, we expect the management team of each LMM portfolio company to have meaningful equity ownership in the portfolio company to better align our respective economic interests. We believe management teams with these attributes are more likely to manage the companies in a manner that both protects our debt investment and enhances the value of our equity investment.



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Established Companies with Positive Cash Flow.  We seek to invest in established companies with sound historical financial performance. We typically focus on LMM companies that have historically generated EBITDA ("Earnings Before Interest, Taxes, Depreciation and Amortization") of $3 million to $20 million and commensurate levels of free cash flow. We also pursue investments in debt securities of Middle Market companies that are generally established companies with sound historical financial performance that are generally larger in size than LMM companies. We generally do not invest in start-up companies or companies with speculative business plans.



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Defensible Competitive Advantages/Favorable Industry Position.  We primarily focus on companies having competitive advantages in their respective markets and/or operating in industries with barriers to entry, which may help to protect their market position and profitability.

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Exit Alternatives.  We exit our debt investments primarily through the repayment of our investment from internally generated cash flow of the portfolio company and/or refinancing. In addition, we seek to invest in companies whose business models and expected future cash flows may provide alternate methods of repaying our investment, such as through a strategic acquisition by other industry participants or a recapitalization.

Investment Portfolio

        The Investment Portfolio, as used herein, refers to all of Main Street's LMM portfolio investments, Middle Market portfolio investments, Private Loan portfolio investments, Other Portfolio investments and the investment in the Investment Manager but excludes all "Marketable securities and idle funds investments." Main Street's LMM portfolio investments principally consist of secured debt, equity warrants and direct equity investments in privately held, LMM companies based in the United States. Main Street's Middle Market portfolio investments primarily consist of direct or secondary investments in interest-bearing debt securities in companies based in the United States that are generally larger in size than the companies included in Main Street's LMM portfolio. Main Street's Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Main Street's Other Portfolio investments primarily consist of investments which are not consistent with the typical profiles for our LMM, Middle Market and Private Loan portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

Debt Investments

        Historically, we have made LMM debt investments principally in the form of single tranche debt. Single tranche debt financing involves issuing one debt security that blends the risk and return profiles of both first lien secured and subordinated debt. We believe that single tranche debt is more appropriate for many LMM companies given their size in order to reduce structural complexity and potential conflicts among creditors.

        Our LMM debt investments generally have terms of three to seven years, with limited required amortization prior to maturity, and provide for monthly or quarterly payment of interest at fixed interest rates generally between 12% and 14% per annum, payable currently in cash. In some instances, we have provided floating interest rates for a portion of a single tranche debt security. In addition, certain LMM debt investments may have a form of interest that is not paid currently but is accrued and added to the loan balance and paid at maturity. We refer to this as payment-in-kind, or PIK, interest. We typically structure our LMM debt investments with the maximum seniority and collateral that we can reasonably obtain while seeking to achieve our total return target. In most cases, our LMM debt investment will be collateralized by a first priority lien on substantially all the assets of the portfolio company. As of March 31, 2013, 93% of our LMM debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies.

        In addition to seeking a senior lien position in the capital structure of our LMM portfolio companies, we seek to limit the downside potential of our LMM investments by negotiating covenants that are designed to protect our LMM investments while affording our portfolio companies as much flexibility in managing their businesses as is reasonable. Such restrictions may include affirmative and negative covenants, default penalties, lien protection, change of control or change of management provisions, key-man life insurance, guarantees, equity pledges, personal guaranties, where appropriate, and put rights. In addition, we typically seek board representation or observation rights in all of our LMM portfolio companies.

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        While we will continue to focus our LMM investments primarily on single tranche debt investments, we also anticipate structuring some of our debt investments as mezzanine loans. We anticipate that these mezzanine loans will be primarily junior secured or unsecured, subordinated loans that provide for relatively high fixed interest rates payable currently in cash that will provide us with significant interest income plus the additional opportunity for income and gains through PIK interest and equity warrants and other similar equity instruments issued in conjunction with these mezzanine loans. These loans typically will have interest-only payments in the early years, with amortization of principal deferred to the later years of the mezzanine loan term. Typically, our mezzanine loans will have maturities of three to five years. We will generally target fixed interest rates of 12% to 14%, payable currently in cash for our mezzanine loan investments with higher targeted total returns from equity warrants or PIK interest.

        We also pursue debt investments in Middle Market companies. Our Middle Market portfolio investments primarily consist of direct or secondary investments in interest-bearing debt securities in companies based in the United States that are generally larger in size than the companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the company and typically have a term of between three and five years. The debt investments in our Middle Market portfolio have rights and protections that are similar to those in our LMM debt investments, which may include affirmative and negative covenants, default penalties, lien protection, change of control provisions, guarantees, and equity pledges. The Middle Market debt investments generally have floating interest rates at LIBOR plus a premium and subject to LIBOR floors. As of March 31, 2013, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 91% of such debt investments at cost were secured by first priority liens on portfolio company assets.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien and typically have a term of between three and seven years. As of March 31, 2013, 99% of Main Street's Private Loan portfolio investments were in the form of debt investments and all such debt investments at cost were secured by first priority liens on portfolio company assets.

Warrants

        In connection with our LMM debt investments, we have historically received equity warrants to establish or increase our equity interest in the LMM portfolio company. Warrants we receive in connection with a LMM debt investment typically require only a nominal cost to exercise, and thus, as a LMM portfolio company appreciates in value, we may achieve additional investment return from this equity interest. We typically structure the warrants to provide provisions protecting our rights as a minority-interest holder, as well as secured or unsecured put rights, or rights to sell such securities back to the LMM portfolio company, upon the occurrence of specified events. In certain cases, we also may obtain registration rights in connection with these equity interests, which may include demand and "piggyback" registration rights.

Direct Equity Investments

        We also will seek to make direct equity investments in situations where it is appropriate to align our interests with key management and stockholders of our LMM portfolio companies, and to allow for some participation in the appreciation in the equity values of our LMM portfolio companies. We usually make our direct equity investments in connection with debt investments. In addition, we may have both equity warrants and direct equity positions in some of our LMM portfolio companies. We

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seek to maintain fully diluted equity positions in our LMM portfolio companies of 5% to 50%, and may have controlling equity interests in some instances. We have a value orientation toward our direct equity investments and have traditionally been able to purchase our equity investments at reasonable valuations.

Investment Process

        Our investment committee is responsible for all aspects of our LMM investment process. The current members of our investment committee are Vincent D. Foster, our Chairman, President and Chief Executive Officer, Todd A. Reppert, our Executive Vice Chairman, and David Magdol, our Chief Investment Officer and Senior Managing Director.

        Our credit committee is responsible for all aspects of our Middle Market portfolio investment process. The current members of our credit committee are Messrs. Foster, Reppert and Curtis Hartman, our Chief Credit Officer and Senior Managing Director.

        Investment process responsibility for each Private Loan portfolio investment is delegated to either the investment committee or the credit committee. Similarly, the investment processes for each Private Loan portfolio investment, from origination to close to eventual exit, will follow the processes for our LMM portfolio investments or our Middle Market portfolio investments as outlined below, or a combination thereof.

        Our investment strategy involves a "team" approach, whereby potential transactions are screened by several members of our investment team before being presented to the investment committee or the credit committee, as applicable. Our investment committee and credit committee each meet on an as needed basis depending on transaction volume. We generally categorize our investment process into seven distinct stages:

Deal Generation/Origination

        Deal generation and origination is maximized through long-standing and extensive relationships with industry contacts, brokers, commercial and investment bankers, entrepreneurs, service providers such as lawyers, financial advisors, accountants and current and former portfolio companies and investors. Our investment team has focused its deal generation and origination efforts on LMM and Middle Market companies. We have developed a reputation as a knowledgeable, reliable and active source of capital and assistance in these markets.

Screening

        During the screening process, if a transaction initially meets our investment criteria, we will perform preliminary due diligence, taking into consideration some or all of the following information:

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a comprehensive financial model based on quantitative analysis of historical financial performance, projections and pro forma adjustments to determine the estimated internal rate of return;



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a brief industry and market analysis;



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direct industry expertise imported from other portfolio companies or investors;



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preliminary qualitative analysis of the management team's competencies and backgrounds;



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potential investment structures and pricing terms; and



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regulatory compliance.

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        Upon successful screening of a proposed LMM transaction, the investment team makes a recommendation to our investment committee. If our investment committee concurs with moving forward on the proposed LMM transaction, we typically issue a non-binding term sheet to the company. For Middle Market portfolio investments, the initial term sheet is typically issued by the borrower, and is screened by the investment team which makes a recommendation to our credit committee.

Term Sheet

        For proposed LMM transactions, the non-binding term sheet will include the key economic terms based upon our analysis performed during the screening process as well as a proposed timeline and our qualitative expectation for the transaction. While the term sheet for LMM investments is non-binding, we typically receive an expense deposit in order to move the transaction to the due diligence phase. Upon execution of a term sheet we begin our formal due diligence process.

        For proposed Middle Market transactions, the initial term sheet will include key economic terms and other conditions proposed by the borrower and its representatives and the proposed timeline for the investment, which are reviewed by our investment team to determine if such terms and conditions are in agreement with Main Street's investment objectives.

Due Diligence

        Due diligence on a proposed LMM investment is performed by a minimum of two of our investment professionals, whom we refer to collectively as the investment team, and certain external resources, who together conduct due diligence to understand the relationships among the prospective portfolio company's business plan, operations and financial performance. Our LMM due diligence review includes some or all of the following:

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site visits with management and key personnel;



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detailed review of historical and projected financial statements;



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operational reviews and analysis;



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interviews with customers and suppliers;



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detailed evaluation of company management, including background checks;



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review of material contracts;



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in-depth industry, market, and strategy analysis;



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regulatory compliance analysis; and



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review by legal, environmental or other consultants, if applicable.

        Due diligence on a proposed Middle Market investment is generally performed on materials and information obtained from certain external resources and assessed internally by a minimum of two of our investment professionals, who work to understand the relationships among the prospective portfolio company's business plan, operations and financial performance using the accumulated due diligence information. Our Middle Market due diligence review includes some or all of the following:

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detailed review of historical and projected financial statements;



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in-depth industry, market, operational and strategy analysis;



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regulatory compliance analysis; and



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detailed review of the company's management team and their capabilities.

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        During the due diligence process, significant attention is given to sensitivity analyses and how the company might be expected to perform given downside, base-case and upside scenarios. In certain cases, we may decide not to make an investment based on the results of the diligence process.

Document and Close

        Upon completion of a satisfactory due diligence review of a proposed LMM portfolio investment, the investment team presents the findings and a recommendation to our investment committee. The presentation contains information which can include, but is not limited to, the following:

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company history and overview;



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transaction overview, history and rationale, including an analysis of transaction strengths and risks;



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analysis of key customers and suppliers and key contracts;



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a working capital analysis;



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an analysis of the company's business strategy;



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a management and key equity investor background check and assessment;



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third-party accounting, legal, environmental or other due diligence findings;



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investment structure and expected returns;



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anticipated sources of repayment and potential exit strategies;



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pro forma capitalization and ownership;



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an analysis of historical financial results and key financial ratios;



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sensitivities to management's financial projections;



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regulatory compliance analysis findings; and



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detailed reconciliations of historical to pro forma results.

        Upon completion of a satisfactory due diligence review of a proposed Middle Market portfolio investment, the investment team presents the findings and a recommendation to our credit committee. The presentation contains information which can include, but is not limited to, the following:

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company history and overview;



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transaction overview, history and rationale, including an analysis of transaction strengths and risks;



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analysis of key customers and suppliers;



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an analysis of the company's business strategy;



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investment structure and expected returns;



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anticipated sources of repayment and potential exit strategies;



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pro forma capitalization and ownership;



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regulatory compliance analysis findings; and



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an analysis of historical financial results and key financial ratios.

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        If any adjustments to the transaction terms or structures are proposed by the investment committee or credit committee, as applicable, such changes are made and applicable analyses are updated prior to approval of the transaction. Approval for the transaction must be made by the affirmative vote from a majority of the members of the investment committee or credit committee, as applicable. Upon receipt of transaction approval, we will re-confirm regulatory compliance, process and finalize all required legal documents, and fund the investment.

Post-Investment

        We continuously monitor the status and progress of the portfolio companies. We generally offer managerial assistance to our portfolio companies, giving them access to our investment experience, direct industry expertise and contacts. The same investment team that was involved in the investment process will continue its involvement in the portfolio company post-investment. This provides for continuity of knowledge and allows the investment team to maintain a strong business relationship with key management of our portfolio companies for post-investment assistance and monitoring purposes. As part of the monitoring process of LMM portfolio investments, the investment team will analyze monthly and quarterly financial statements versus the previous periods and year, review financial projections, meet and discuss issues or opportunities with management, attend board meetings and review all compliance certificates and covenants. While we maintain limited involvement in the ordinary course operations of our LMM portfolio companies, we maintain a higher level of involvement in non-ordinary course financing or strategic activities and any non-performing scenarios. We also monitor the performance of our Middle Market portfolio investments; however, due to the larger size and higher sophistication level of these Middle Market companies in comparison to our LMM portfolio companies, it is not necessary or practical to have as much direct management interface.

        We utilize an internally developed investment rating system to rate the performance of each LMM portfolio company and to monitor our expected level of returns on each of our LMM investments in relation to our expectations for the portfolio company. The investment rating system takes into consideration various factors, including, but not limited to, each investment's expected level of returns and the collectability of our debt investments, comparisons to competitors and other industry participants and the portfolio company's future outlook.

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Investment Rating 1 represents a portfolio company that is performing in a manner which significantly exceeds expectations;



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Investment Rating 2 represents a portfolio company that, in general, is performing above expectations;



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Investment Rating 3 represents a portfolio company that is generally performing in accordance with expectations;



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Investment Rating 4 represents a portfolio company that is underperforming expectations. Investments with such a rating require increased Main Street monitoring and scrutiny; and



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Investment Rating 5 represents a portfolio company that is significantly underperforming. Investments with such a rating require heightened levels of monitoring and scrutiny by us and involve the recognition of significant unrealized depreciation on such investment.

        All new LMM portfolio investments receive an initial 3 rating.

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        The following table shows the distribution of our LMM portfolio investments on the 1 to 5 investment rating scale at fair value as of March 31, 2013 and December 31, 2012:

        Based upon our investment rating system, the weighted average rating of our LMM portfolio was approximately 2.2 as of March 31, 2013 and 2.1 as of December 31, 2012.

        For the total Investment Portfolio, as of March 31, 2013, we had one investment with positive fair value on non-accrual status which comprised 0.2% of the total Investment Portfolio at fair value and, together with another fully impaired investment, comprised approximately 0.7% of the total Investment Portfolio at cost, excluding the investment in the affiliated Investment Manager. As of December 31, 2012, we had no investments with positive fair value on non-accrual status and one fully impaired investment which comprised approximately 0.2% of the total Investment Portfolio at cost, excluding the investment in the affiliated Investment Manager.

Exit Strategies/Refinancing

        While we generally exit most investments through the refinancing or repayment of our debt and redemption of our equity positions, we typically assist our LMM portfolio companies in developing and planning exit opportunities, including any sale or merger of our portfolio companies. We may also assist in the structure, timing, execution and transition of the exit strategy. The refinancing or repayment of Middle Market debt investments typically does not require our assistance due to the additional resources available to these larger, Middle Market companies.

Determination of Net Asset Value and Portfolio Valuation Process

        We determine the net asset value per share of our common stock on a quarterly basis. The net asset value per share is equal to our total assets minus liabilities and any noncontrolling interests outstanding divided by the total number of shares of common stock outstanding.

        The most significant determination inherent in the preparation of our consolidated financial statements is the valuation of our Investment Portfolio and the related amounts of unrealized appreciation and depreciation. As of March 31, 2013 and December 31, 2012, approximately 96% and 89%, respectively, of our total assets at each date represented investments in portfolio companies valued at fair value (including our investment in the Investment Manager). We are required to report our investments at fair value. We follow the provisions of the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("Codification" or "ASC") 820, Fair Value Measurements and Disclosures ("ASC 820"). ASC 820 defines fair value, establishes a framework for measuring fair value, establishes a fair value hierarchy based on the quality of inputs used to measure fair value, and enhances disclosure requirements for fair value measurements.

        Our business strategy calls for us to invest primarily in illiquid debt and equity securities issued by private, LMM companies and debt securities issued by Middle Market companies that are generally larger in size than the LMM companies. We also categorize some of our investments in LMM

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companies and Middle Market companies as Private Loan portfolio investments, which are typically debt securities issued by companies that are consistent in size with either the LMM companies or Middle Market companies, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Our portfolio also includes Other Portfolio investments which primarily consist of investments which are not consistent with the typical profiles for our LMM portfolio investments, Middle Market portfolio investments or Private Loan portfolio investments, including investments which may be managed by third parties. All of these portfolio investments may be subject to restrictions on resale.

        LMM investments and Other Portfolio investments generally have no established trading market while Middle Market securities generally have established markets that are not active. Private Loan investments may include investments which have no established trading market or have established markets that are not active. We determine in good faith the fair value of our Investment Portfolio pursuant to a valuation policy in accordance with ASC 820 and a valuation process approved by our Board of Directors and in accordance with the 1940 Act. Our valuation policy and process is intended to provide a consistent basis for determining the fair value of our portfolio.

        For LMM investments, we review external events, including private mergers, sales and acquisitions involving comparable companies, and include these events in the valuation process. For Middle Market portfolio investments, we primarily use observable inputs such as quoted prices in the valuation process. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we generally use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        For valuation purposes, "control" LMM portfolio investments are composed of debt and equity securities in companies for which we have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for our control LMM portfolio investments. As a result, for control LMM portfolio investments, we determine the fair value using a combination of market and income approaches. Under the market approach, we will typically use the enterprise value methodology to determine the fair value of these investments. The enterprise value is the fair value at which an enterprise could be sold in a transaction between two willing parties, other than through a forced or liquidation sale. Typically, private companies are bought and sold based on multiples of earnings before interest, taxes, depreciation and amortization, or EBITDA, cash flows, net income, revenues, or in limited cases, book value. There is no single methodology for estimating enterprise value. For any one portfolio company, enterprise value is generally described as a range of values from which a single estimate of enterprise value is derived. In estimating the enterprise value of a portfolio company, we analyze various factors, including the portfolio company's historical and projected financial results. We allocate the enterprise value to investments in order of the legal priority of the various components of the portfolio company's capital structure. We will also use the income approach to determine the fair value of these securities, based on projections of the discounted future free cash flows that the portfolio company or the debt security will likely generate, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments.. The valuation approaches for our control LMM portfolio investments estimate the value of the investment if we were to sell, or exit, the investment. In addition, these valuation approaches consider the value associated with our ability to control the capital structure of the portfolio company, as well as the timing of a potential exit.

        For valuation purposes, "non-control" LMM portfolio investments are composed of debt and equity securities in companies for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations

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are generally not readily available for non-control LMM portfolio investments. For our non-control LMM investments, we use a combination of the market and income approaches to value our equity investments and the income approach to value our debt investments similar to the approaches used for our control LMM portfolio investments, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. Our estimate of the expected repayment date of a LMM debt security is generally the legal maturity date of the instrument, as we generally intend to hold our LMM loans and debt securities to maturity. The yield-to-maturity analysis considers changes in leverage levels, credit quality, portfolio company performance and other factors. We will use the value determined by the yield-to-maturity analysis as the fair value for that security; however, because of our general intent to hold our loans to maturity, the fair value will not exceed the face amount of the LMM debt security. A change in the assumptions that we use to estimate the fair value of our LMM debt securities using the yield-to-maturity analysis could have a material impact on the determination of fair value. If there is deterioration in credit quality or if a LMM debt security is in workout status, we may consider other factors in determining the fair value of the LMM debt security, including the value attributable to the debt security from the enterprise value of the portfolio company or the proceeds that would most likely be received in a liquidation analysis.

        Our Middle Market portfolio investments primarily consist of direct or secondary investments in interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our Investment Portfolio. For valuation purposes, all of our Middle Market portfolio investments are non-control investments for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. We primarily use observable inputs to determine the fair value of these investments through obtaining third party quotes or independent pricing, to the extent such sufficient observable inputs are available to determine fair value. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        Our Private Loan portfolio investments primarily consist of direct or secondary investments in interest-bearing debt securities in companies that are consistent with the size of companies included in our LMM portfolio or our Middle Market portfolio. For valuation purposes, all of Main Street's Private Loan portfolio investments are non-control investments for which Main Street does not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. As sufficient observable inputs to determine the fair value of these Private Loan portfolio investments through obtaining third party pricing or other independent pricing are not generally available, Main Street generally uses a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value its LMM portfolio debt investments.

        For valuation purposes, all of our Other Portfolio investments are non-control investments for which we generally do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Main Street's Other Portfolio investments comprised 2.9% and 2.6%, respectively, of Main Street's Investment Portfolio at fair value as of March 31, 2013 and December 31, 2012. Similar to the LMM investment portfolio, market quotations for Other Portfolio equity investments are generally not readily available. For our Other Portfolio equity investments, we determine the fair value based on the fair value of the portfolio company as determined by independent third parties and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. For Other Portfolio debt investments with observable inputs, we determine the fair value

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of these investments through obtaining third party quotes or other independent pricing, to the extent such sufficient observable inputs are available to determine fair value. To the extent observable inputs are not available, we value these Other Portfolio debt investments through an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        Due to the inherent uncertainty in the valuation process, our determination of fair value for our Investment Portfolio may differ materially from the values that would have been used had a ready market for the securities existed. In addition, changes in the market environment, portfolio company performance and other events that may occur over the lives of the investments may cause the gains or losses ultimately realized on these investments to be materially different than the valuations currently assigned. We determine the fair value of each individual investment and record changes in fair value as unrealized appreciation or depreciation.

        As described below, we undertake a multi-step valuation process each quarter in connection with determining the fair value of our investments, with our Board of Directors having final responsibility for overseeing, reviewing and approving, in good faith, our determination of the fair value of each individual investment.

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Our quarterly valuation process begins with each LMM portfolio company or investment being initially valued by the investment team responsible for the portfolio investment;



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The fair value determination for our Middle Market, Private Loan and Other Portfolio debt investments generally consists of observable inputs which are initially reviewed by the investment professionals responsible for the portfolio investment;



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Preliminary valuation conclusions are then reviewed by and discussed with senior management, and the investment team considers and assesses, as appropriate, any changes that may be required to the preliminary valuations to address any comments provided by senior management;



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As described above, a nationally recognized independent advisor engaged by the Board of Directors performs certain mutually agreed limited procedures that we and the Board of Directors have identified and asked them to perform on a selection of management's LMM portfolio company valuation conclusions;



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The Audit Committee of our Board of Directors reviews management's valuations, and the investment team and senior management consider and assess, as appropriate, any changes that may be required to management's valuations to address any comments provided by the Audit Committee; and



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The Board of Directors assesses the valuations and ultimately approves the fair value of each investment in our portfolio in good faith.

        Determination of fair value involves subjective judgments and estimates. The notes to our financial statements will refer to the uncertainty with respect to the possible effect of such valuations, and any change in such valuations, on our financial statements.

Competition

        We compete for investments with a number of investment funds (including private equity funds, mezzanine funds, BDCs, and SBICs), as well as traditional financial services companies such as commercial banks and other sources of financing. Many of the entities that compete with us have greater financial and managerial resources. We believe we are able to be competitive with these entities primarily on the basis of our focus toward the underserved LMM, the experience and contacts of our management team, our responsive and efficient investment analysis and decision-making processes, our comprehensive suite of customized financing solutions and the investment terms we offer.

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        We believe that some of our competitors make senior secured loans, junior secured loans and subordinated debt investments with interest rates and returns that are comparable to or lower than the rates and returns that we target. Therefore, we do not seek to compete primarily on the interest rates and returns that we offer to potential portfolio companies. For additional information concerning the competitive risks we face, see "Risk Factors—Risks Related to Our Business and Structure—We may face increasing competition for investment opportunities."

Employees

        As of March 31, 2013, we had 34 employees, each of whom was employed by the Investment Manager. These employees include investment and portfolio management professionals, operations professionals and administrative staff. As necessary, we will hire additional investment professionals and administrative personnel. All of our employees are located in our Houston, Texas office.

Properties

        We do not own any real estate or other physical properties materially important to our operations. Currently, we lease office space in Houston, Texas for our corporate headquarters.

Legal Proceedings

        We may, from time to time, be involved in litigation arising out of our operations in the normal course of business or otherwise. Furthermore, third parties may try to seek to impose liability on us in connection with the activities of our portfolio companies. While the outcome of any current legal proceedings cannot at this time be predicted with certainty, we do not expect any current matters will materially affect our financial condition or results of operations; however, there can be no assurance whether any pending legal proceedings will have a material adverse effect on our financial condition or results of operations in any future reporting period.

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PORTFOLIO COMPANIES

        The following table sets forth certain unaudited information as of March 31, 2013, for the portfolio companies in which we had a debt or equity investment. Other than these investments, our only formal relationships with our portfolio companies are the managerial assistance ancillary to our investments and the board observer or participation rights we may receive. As of March 31, 2013, none of our portfolio company investments constituted five percent or more of our total assets. The following table excludes our investment in the Investment Manager and marketable securities and idle funds investments.

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