UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 11-K

þ		ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2007

o		TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                      to                     

A.	Savings and Profit Sharing Plan for Employees of First Interstate BancSystem, Inc.
		(Full title of the plan)

Same as below

B.		First Interstate BancSystem, Inc.
		(Name of issuer of the securities held pursuant to the plan)

(Address of issuer’s principal executive office)

 

 

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF
FIRST INTERSTATE BANCSYSTEM, INC.

FINANCIAL STATEMENTS
DECEMBER 31, 2007 AND 2006

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.

Table of Contents

		Page
REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM			1
FINANCIAL STATEMENTS
Statements of Net Assets Available for Benefits			2
Statement of Changes in Net Assets Available for Benefits			3
Notes to Financial Statements			4-10
SUPPLEMENTARY INFORMATION
Schedule H, Line 4i — Schedule of Assets (Held at End of Year)			11

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Executing Committee of the
Savings and Profit Sharing Plan for Employees of First Interstate BancSystem, Inc.
Billings, Montana

We have audited the accompanying statements of net assets available for plan benefits of the Savings and Profit Sharing Plan for Employees of First Interstate BancSystem, Inc. (the “Plan”) as of December 31, 2007 and 2006, and the related statement of changes in net assets available for plan benefits for the year ended December 31, 2007. These financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement. The Plan is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. Our audits included consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Plan’s internal control over financial reporting. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly in all material respects, the net assets available for plan benefits of the Savings and Profit Sharing Plan for Employees of First Interstate BancSystem, Inc. as of December 31, 2007 and 2006, and the changes in net assets available for plan benefits for the year ended December 31, 2007 in conformity with accounting principles generally accepted in the United States of America.

Our audits were performed for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedule of assets held at end of year as of December 31, 2007 is presented for the purpose of additional analysis and is not a required part of the basic financial statements but is supplementary information required by the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. This supplemental schedule is the responsibility of the Plan’s management. The supplemental schedule has been subjected to the auditing procedures applied in the audit of the 2007 basic financial statements and, in our opinion, is fairly stated in all material respects in relation to the basic financial statements taken as a whole.

                     /s/ Gordon, Hughes & Banks, LLP

Greenwood Village, Colorado
June 19, 2008

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.

		2007				2006
ASSETS
Investments, at fair value
Registered investment companies		$	95,767,274			$	85,179,908
Collective trust fund			4,160,714				—
Employer securities			53,018,726				52,613,633
Participant loans			2,037,914				1,553,901
			154,984,628				139,347,442
Receivables
Employer’s contributions			609,216				1,060,327
Employees’ contributions			—				—
Accrued interest on loan payments			—				—
Accrued investment income			—				—
			609,216				1,060,327
Noninterest-bearing cash			275,376				—
NET ASSETS AVAILABLE FOR BENEFITS, AT FAIR VALUE		$	155,869,220			$	140,407,769
Adjustment from fair value to contract value for fully benefit-responsive investment contract			11,865				—
NET ASSETS AVAILABLE FOR BENEFITS		$	155,881,085			$	140,407,769

See notes to financial statements.		2

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.

Additions to net assets attributed to:
Investment income
Net appreciation in fair value of investments		$	9,781,151
Dividends			1,875,732
Interest			144,557
			11,801,440
Contributions
Employer			5,973,973
Participants’			5,457,174
Rollovers			1,303,499
			12,734,646
Total additions			24,536,086
Deductions from net assets attributed to:
Benefits paid to participants			8,760,260
Fees paid from plan assets			302,510
Total deductions			9,062,770
Net increase			15,473,316
Net assets available for benefits:
Beginning of year			140,407,769
End of year		$	155,881,085

See notes to financial statements.		3

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.

NOTE 1 — DESCRIPTION OF PLAN AND SIGNIFICANT ACCOUNTING POLICIES

Description of Plan

The following description of the First Interstate BancSystem, Inc. (the “Company”) Savings and Profit Sharing Plan for Employees of First Interstate BancSystem, Inc. (the “Plan”) provides only general information. Participants should refer to the Summary Plan Description for a more complete description of the Plan’s provisions.

General. The Plan is a defined contribution plan covering all employees of the Company’s member banks and affiliates who are classified as regular-status scheduled to work 20 hours or more per week, or, if not classified as regular status have completed 1,000 hours of service in no more than twelve consecutive months. It is subject to the provisions of the Employee Retirement Income Security Act of 1974 (ERISA).

Elective and Matching Contributions. At initial entry in the Plan, participants are automatically enrolled to contribute four percent of their annual compensation in pre-tax contributions, unless they elect otherwise. Participants may change their elective contribution rate as of any pay period by filing a new election. Such elective contributions are limited to the annual limitation defined in Internal Revenue Code Section 402(g)(1), which was $15,500 for 2007 and $15,500 for 2006. Participants aged 50 or older before the close of the Plan year are eligible to make catch-up contributions in accordance with, and subject to the limitations of, Section 414(v) of the Code. Participants may also contribute amounts representing distributions from other qualified defined benefit or contribution plans.

The Company makes a matching contribution of 125 percent of the first four percent of annual compensation that a participant contributes to the Plan.

Discretionary Contributions. At its discretion, the Company may make a quarterly profit sharing contribution. The Plan also allows for an Applicable Minimum Employer contribution and a Specified Minimum Employer contribution as determined by the Company’s board of directors by appropriate resolution on or before the last day of the Company’s tax year.

Participant Accounts. Each participant’s account is credited with the participant’s contributions and allocations of the Company contributions and Plan earnings. Allocations of participant earnings are based on account balances, as defined. Forfeited balances of terminated participants’ nonvested accounts are used to pay administrative expenses incurred by the Plan. The benefit to which a participant is entitled is the benefit that can be provided from the participant’s vested account.

(continued on next page)		4

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2007 AND 2006

Vesting. Participants are immediately vested in their contributions and any rollover contributions plus allocated earnings thereon. Vesting in the Company’s matching and profit sharing contribution portions of their accounts and earnings thereon is contingent upon the participant’s date of hire. Employees who were hired before January 1, 2000 and participating in the Plan before January 1, 2001 are 100 percent vested in the Company’s matching and profit sharing contributions. Employees who were hired as regular-status working 20 hours or more per week during the fiscal year 2000 and became participants in fiscal year 2001 after completing 1 year of service, as defined, are also 100 percent vested in the Company’s matching and profit sharing contributions. Employees hired in fiscal year 2001 or later are subject to a vesting schedule based on years of service. These participants are 100 percent vested in the Company’s matching and profit sharing contributions after three years of credited service.

Participant loans. Loans are limited to the lesser of (a) 50 percent of the participant’s vested account balance or (b) $50,000, reduced by the excess, if any, of (i) the participant’s highest outstanding loan balance during the previous year, over (ii) the participant’s outstanding loan balance on the date the loan is made. Loan terms shall not exceed the earlier of (a) 15 years if the loan is for the purchase of a principal residence of the borrower or (b) five years for all other loans. The loans are secured by the balance in the participant’s account and bear a rate of interest which is commensurate with the interest rates being charged at the time such loan is made under similar circumstances by financial institutions in the community in which the Company’s principal office is then located. Interest rates on the participant loans outstanding at December 31, 2007 ranged from 5.0 percent to 10.5 percent. Principal and interest is paid ratably through biweekly payroll deductions for active employees.

Investment Options. Upon enrollment in the Plan, a participant may direct contributions in a variety of mutual fund offerings of registered investment companies. The most common options as of December 31, 2007 are as follows:

Accessor Balanced Allocation Fund – Funds are divided between equity funds and fixed-income funds in approximate equal proportion.

Accessor Growth Allocation Fund – Funds are invested primarily in equity funds and some fixed-income funds with a target range of approximately 80% and 20%, respectively.

Harbor International Fund – Funds are invested primarily in equity securities, principally common and preferred stocks of foreign companies located in Europe, the Pacific Basin and emerging industrialized countries whose economics and political regimes appear more stable and are believed to provide some protection to foreign shareholders.

Accessor Aggressive Growth Allocation Fund – Funds are invested in the domestic and international equity markets.

Accessor Growth & Income Allocation Fund – Funds are invested in equity funds and some fixed-income funds with a target range of approximately 60% and 40%, respectively.

Fidelity Spartan U.S. Equity Index Fund – Funds are invested primarily in common stocks included in the Standard & Poor’s 500 Index, which broadly represents the performance of common stocks publicly traded in the United States.

MetLife Stable Value Fund – Funds are invested in U.S. government and agency securities, asset-backed securities, mortgage-backed securities and U.S. large company stocks. The fund is guaranteed through MetLife to maintain the value of principal and all accumulated interest.

(continued on next page)		5

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2007 AND 2006

A participant may not contribute to, but may direct transfers from any investment into, the following investment option:

First Interstate BancSystem, Inc. Stock – Funds are invested in First Interstate BancSystem, Inc. stock (Company Stock). A participant’s investment in Company Stock is limited to 50 percent of the participant’s account balance, as defined.

As of December 31, 2007 and 2006, Plan assets invested in Company Stock were 34 percent and 38 percent of net assets available for benefits, respectively.

Payment of Benefits. After termination of service due to death, disability, or retirement, a participant with an account balance of more than $5,000 may, on any distribution date following termination, elect to receive either a lump sum distribution of his/her vested account balance or installment payments (annually, quarterly, or monthly) of a specific dollar amount not to exceed 10% of the account balance at the time of election or installment payments over a specified period of time not to exceed the participant’s life expectancy or an installment in an amount equal to the required minimum distribution for the year. Any participant account balance with less than $5,000 is distributed in a lump sum. For termination of service due to other reasons, a participant may receive the value of the vested interest in his/her account as a lump sum distribution. A participant may elect to receive a hardship distribution, without termination of employment, if he/she qualifies under the hardship withdrawal rules.

Member Employers. Members of the Plan include First Interstate BancSystem, Inc. and the following Subsidiaries:

First Interstate Bank
i_Tech Corporation
FIBCT, LLC
* Commerce Financial, Inc.
* FI Reinsurance, Ltd.
* First Interstate Statutory Trust
* FIB, LLC
* FI Insurance Agency

*    Denotes no current employees

Forfeited Accounts. At December 31, 2007 and 2006, forfeited non-vested accounts totaled $113,789 and $163,381, respectively. These accounts will be used first to administrative expenses incurred by the Plan. During the year ended December 31, 2007, $302,510 was used to pay Plan expenses.

Basis of Accounting

The accompanying financial statements have been prepared on an accrual basis and present the net assets available for participant benefits and changes in those net assets.

(continued on next page)		6

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2007 AND 2006

Use of Estimates

The preparation of financial statements in conformity with standards of the Public Company Accounting Oversight Board (United States) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Investment Valuation and Income Recognition

The Plan’s investments in the mutual funds of registered investment companies are valued at quoted market prices. The collective trust fund’s estimated fair value and contract value is based on the underlying benefit-responsive investment contract with MetLife Insurance Company, as reported by the fund’s trustee. Company Stock is valued based on an independent appraisal prepared by Alex Sheshunoff & Co. Investment Banking. The appraised fair market value of a share of Company Stock was $87.75 and $82.50 as of September 30, 2007 and 2006, respectively, which values were the most current valuations of Company Stock available on December 31, 2007 and 2006, respectively.

Purchases and sales of securities are recorded on a trade-date basis. Interest income is recorded on the accrual basis. Dividends are recorded on the ex-dividend date.

Risks and Uncertainties

The Plan invests in various investment securities. Investment securities are exposed to various risks such as interest rate, market, and credit risks. Due to the level of risk associated with certain investment securities, it is at least reasonably possible that changes in the values of investment securities will occur in the near term and that such changes could materially affect participants’ account balances and the amounts reported in the statement of net assets available for benefits.

Payment of Benefits

Benefits are recorded when paid.

Adoption of New Pronouncement

As described in the Financial Accounting Standards Board Staff Position, FSP Nos. AAG INV-1 and SOP 94-4-1, Reporting of Fully Benefit-Responsive Investment Contracts Held by Certain Investment Companies Subject to the AICPA Investment Company Guide and Defined-Contribution Health and Welfare and Pension Plans (“FSP”), investment contracts held by a defined contribution plan are required to be reported at fair value. However, contract value is the relevant measurement attribute for that portion of the net assets available for benefits of a plan attributable to fully benefit-responsive investment contracts because contract value is the amount participants would receive if they were to initiate permitted transactions under the terms of the plan. As required by the FSP, the Statement of Net Assets Available for Benefits as of December 31, 2007, which is when the investment was first purchased, presents the adjustment of the investment contract from fair value to contract value. The Statement of Changes in Net Assets Available for Benefits is prepared on contract value basis. No retroactive application of the FSP is necessary, as the asset was not owned as of December 31, 2006.

(continued on next page)		7

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2007 AND 2006

Income Tax Status

The Plan obtained its latest determination letter dated July 2, 2003, in which the Internal Revenue Service (IRS) stated that the Plan, as then designed, was in compliance with the applicable requirements of Internal Revenue Code (IRC). Although the Plan has been amended since receiving the determination letter, the Plan administrator and the Plan’s counsel believe the Plan is designed and is currently operated in compliance with the applicable requirements of the IRC.

NOTE 2 – INVESTMENTS

The following presents the individual investments (all participant-directed) that represent 5 percent or more of the Plan assets available for benefits:

		2007								2006
		Number								Number
		of units				Fair Value				of units				Fair Value
Registered investment companies, fair value as determined by quoted market price:
Accessor Balanced Allocation Fund			1,046,290			$	18,090,355				905,043			$	15,512,431
Accessor Growth Allocation Fund			754,740				14,098,550				724,468				13,192,562
Harbor International Fund			194,170				13,855,954				175,913				10,913,627
Accessor Aggressive Growth Allocation Fund			583,729				11,371,034				556,804				10,473,486
Accessor Growth & Income Allocation Fund			509,717				9,032,192				479,943				8,394,202
Employer securities, fair value as determined by appraisal:
First Interstate BancSystem, Inc. Stock			604,202				53,018,726				637,741				52,613,633
						$	119,466,811							$	111,099,941
During 2007, the Plan’s investments (including gains and losses on investments bought and sold, as well as held during the year) appreciated in value by $9,781,151 as follows:
Investments at fair value as determined by quoted market price:
Registered investment companies						$	6,450,411
Investments at fair value as determined by appraisal:
Employer securities							3,330,740
						$	9,781,151

(continued on next page)		8

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2007 AND 2006

NOTE 3 – ADMINISTRATIVE EXPENSES

First Interstate Financial Services Group serves as trustee of the Plan. Fidelity Investments Institutional Brokerage Group holds custody of the Plan’s assets. Rocky Mountain Employee Benefits, Inc. performs the recordkeeping for the Plan. The Plan pays the administrative fees related to these services performed for the Plan from the forfeited balances of the nonvested portion of terminated participant’s account balances. The Company pays any other administrative expenses related to the plan.

NOTE 4 – PLAN TERMINATION

Although the Company has not expressed any intent to do so, it has the right to terminate the Plan subject to the provisions of ERISA. In the event of Plan termination, participants will become 100 percent vested in their accounts.

NOTE 5 – PARTY-IN-INTEREST TRANSACTIONS

Fees are charged to the participant for the processing of loans and distributions. These fees totaled $28,529 for the year ended December 31, 2007. These fees are considered customary and reasonable for such services.

Some Plan assets are invested in shares of the common stock of First Interstate BancSystem, Inc. by participant direction. These transactions qualify as party-in-interest.

Certain Plan investments are shares of mutual funds managed by Fidelity Management & Research, which is an affiliate of the plan’s custodian, Fidelity Investments Institutional Brokerage Group. In this custodial capacity, Fidelity has no fiduciary responsibility to the Plan. However, these transactions could qualify as party-in-interest should some change occur in this relationship.

NOTE 6 – PLAN AMENDMENTS

Effective January 1, 2007 the Plan was amended to allow a direct rollover to an individual retirement account for a non-spouse Beneficiary of a participant.

Prior to March 1, 2007, a Distribution Date was defined as the business day coinciding with or next following the fifteenth day of each calendar month. Effective March 1, 2007, the Plan was amended to define a Distribution Date for purposes of distributions of Investment Funds other than the Company stock as the business day with or next following the fifteenth day of each calendar month. For purposes of distributions of Company stock, the Distribution Date is the 15^th day of the second month following the end of each calendar quarter.

Effective June 1, 2007, the Plan was amended to reduce the maximum investment in Company Stock, at the time of election, to no more than 25% of the participant’s account balance, less any balance attributable to rollover contributions.

(continued on next page)		9

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2007 AND 2006

NOTE 7 – RECONCILIATION OF FINANCIAL STATEMENTS TO FORM 5500

The following is a reconciliation of net assets available for benefits per the financial statements at December 31, 2007 and 2006 to Form 5500:

		2007				2006
Net assets available for benefits per the financial statements		$	155,881,085			$	140,407,769
Fair value of fully benefit-responsive investment			(11,865	)			—
Participant loan balance deemed distributed			(7,037	)			(6,610	)
Net assets available for benefits per the Form 5500		$	155,862,183			$	140,401,159

The following is a reconciliation of changes in net assets available for benefits per the financial statements for the year ended December 31, 2007:

		2007
Net increase per the financial statements		$	15,473,316
Depreciation in fully benefit responsive investment			(11,865	)
Deemed distribution of participant loan accrued interest			(427	)
Net increase per the Form 5500		$	15,461,024

		10

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF
FIRST INTERSTATE BANCSYSTEM, INC.

SUPPLEMENTARY INFORMATION

SAVINGS AND PROFIT SHARING PLAN
FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.

EIN 81-0331430
PN 003

				(c) Description of investment
				including maturity date, rate of
		(b) Identity of issue, Borrower,		interest, collateral, par or maturity
(a)		lessor, or similar party		value		(d) Cost		(e) Current Value
*		First Interstate BancSystem, Inc.		Employer securities, 604,202 common shares		N/A		$	53,018,726
		Accessor Capital Management		Balanced Allocation Fund, mutual fund		N/A			18,090,355
		Accessor Capital Management		Growth Allocation Fund, mutual fund		N/A			14,098,550
		Accessor Capital Management		Aggressive Growth Allocation Fund, mutual fund		N/A			11,371,034
		Accessor Capital Management		Growth & Income Allocation Fund, mutual fund		N/A			9,032,192
		Harbor Capital Advisors		Harbor International Fund, mutual fund		N/A			13,855,954
**		Fidelity Management & Research		Spartan U.S. Equity Index Fund, mutual fund		N/A			5,177,044
**		Fidelity Management & Research		Money Market Fund, mutual fund		N/A			2,798,738
		Accessor Capital Management		Growth Fund, mutual fund		N/A			2,891,157
		Davis Funds		Davis New York Venture, mutual fund		N/A			3,026,152
		Accessor Capital Management		Small to Mid Cap Fund, mutual fund		N/A			2,320,626
		Franklin Templeton Investments		Small-Mid Cap Growth Fund, mutual fund		N/A			2,060,817
		T Rowe Price Associates, Inc.		Equity Income Fund, mutual fund		N/A			2,353,863
		Luther King Capital Management Corp.		Small Cap Equity Fund, mutual fund		N/A			1,343,847
*		Participant Loans		Interest Rates ranging from 5% to 10.5%		0			2,037,914
**		Fidelity Management & Research		Advisor Equity Growth Fund, mutual fund		N/A			2,656,030
		Vanguard Group		Intermediate Term Treasury Admiral Fund, mutual fund		N/A			1,001,780
**		Fidelity Management & Research		Government Income Fund, mutual fund		N/A			630,854
		Accessor Capital Management		Income & Growth Allocation Fund, mutual fund		N/A			1,162,292
		Dodge & Cox		Dodge & Cox Income Fund, mutual fund		N/A			811,480
		Accessor Capital Management		Income Allocation Fund, mutual fund		N/A			626,725
		Vanguard Group		Small Cap Stock Index Trust Fund, mutual fund		N/A			325,249
		Metropolitan Life Insurance Company		MetLife Stable Value Fund, GIC		N/A			4,160,714
**		Fidelity Cash Reserves		Money Market Fund		N/A			132,535
								$	154,984,628

		11

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees have duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized.

SAVINGS AND PROFIT SHARING PLAN FOR EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.

June 24, 2008				/s/ LYLE R. KNIGHT
Date				Lyle R. Knight, Chairman
				First Interstate BancSystem, Inc. Benefits Committee,
				Plan Administrator of the Savings and Profit Sharing
				Plan for Employees of First Interstate BancSystem, Inc.

First Interstate BancSystem, Inc.

EXHIBIT INDEX

Exhibit		Document
23.1		Consent of Gordon, Hughes & Banks, LLP, Independent Registered Public Accounting Firm.