Form N-Q

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

FORM N-Q


QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED MANAGEMENT INVESTMENT COMPANY

Investment Company Act file number         811-6623         

        Nuveen California Select Tax-Free Income Portfolio         
(Exact name of registrant as specified in charter)

Nuveen Investments
        333 West Wacker Drive, Chicago, Illinois 60606         
(Address of principal executive offices) (Zip code)


Kevin J. McCarthy—Vice President and Secretary
        333 West Wacker Drive, Chicago, Illinois 60606         
(Name and address of agent for service)

Registrant's telephone number, including area code:         312-917-7700        

Date of fiscal year end:            3/31          

Date of reporting period:         6/30/07         

Form N-Q is to be used by management investment companies, other than small business investment companies registered on Form N-5 (§§ 239.24 and 274.5 of this chapter), to file reports with the Commission, not later than 60 days after the close of the first and third fiscal quarters, pursuant to rule 30b1-5 under the Investment Company Act of 1940 (17 CFR 270.30b1-5). The Commission may use the information provided on Form N-Q in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-Q, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-Q unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to the Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. § 3507.

Item 1. Schedule of Investments

    Portfolio of Investments (Unaudited)             
    Nuveen California Select Tax-Free Income Portfolio (NXC)             
    June 30, 2007             
Principal        Optional Call         
Amount (000)    Description    Provisions (1)    Ratings (2)    Value 
    Consumer Staples – 5.3%             
$             220    California County Tobacco Securitization Agency, Tobacco Settlement Asset-Backed Bonds, Sonoma    6/15 at 100.00    BBB   $   213,286 
     County Tobacco Securitization Corporation, Series 2005, 4.250%, 6/01/21             
1,505    California County Tobacco Securitization Agency, Tobacco Settlement Asset-Backed Revenue    6/12 at 100.00    BBB    1,518,936 
     Bonds, Fresno County Tobacco Funding Corporation, Series 2002, 5.625%, 6/01/23             
4,045    Golden State Tobacco Securitization Corporation, California, Enhanced Tobacco Settlement    6/22 at 100.00    BBB    3,073,351 
     Asset-Backed Bonds, Series 2007A-2, 0.000%, 6/01/37             
5,770    Total Consumer Staples            4,805,573 
    Education and Civic Organizations – 10.4%             
1,000    California Educational Facilities Authority, Revenue Bonds, Stanford University, Series 1999P,    12/09 at 101.00    AAA    1,029,820 
     5.000%, 12/01/23             
45    California Educational Facilities Authority, Revenue Bonds, University of Redlands, Series    10/15 at 100.00    A3    45,881 
     2005A, 5.000%, 10/01/35             
1,000    California Educational Facilities Authority, Revenue Bonds, University of San Diego, Series    10/12 at 100.00    A2    1,050,470 
     2002A, 5.500%, 10/01/32             
    California Educational Facilities Authority, Revenue Bonds, University of the Pacific, Series 2006:             
35     5.000%, 11/01/21    11/15 at 100.00    A2    36,265 
45     5.000%, 11/01/25    11/15 at 100.00    A2    46,248 
3,000    California Infrastructure Economic Development Bank, Revenue Bonds, J. David Gladstone    10/11 at 101.00    A–    3,147,930 
     Institutes, Series 2001, 5.500%, 10/01/19             
2,000    California State Public Works Board, Lease Revenue Bonds, University of California, UCLA    10/12 at 100.00    AAA    2,058,000 
     Replacement Hospital Project, Series 2002A, 5.000%, 10/01/22 – FSA Insured             
1,000    Long Beach Bond Financing Authority, California, Lease Revenue Refunding Bonds, Long Beach    11/11 at 101.00    AAA    1,038,310 
     Aquarium of the South Pacific, Series 2001, 5.250%, 11/01/30 – AMBAC Insured             
1,000    University of California System, General Revenue Bonds, Series 2006J, 4.500%, 5/15/35 (WI/DD,    5/15 at 101.00    AAA    959,300 
     Settling 7/05/07) – FSA Insured             
9,125    Total Education and Civic Organizations            9,412,224 
    Health Care – 13.9%             
670    California Health Facilities Financing Authority, Revenue Bonds, Cedars-Sinai Medical Center,    11/15 at 100.00    A2    675,440 
     Series 2005, 5.000%, 11/15/34             
2,550    California Health Facilities Financing Authority, Revenue Bonds, Sutter Health,    11/16 at 100.00    AA–    2,626,551 
     Series 2007A, 5.250%, 11/15/46 (UB)             
2,000    California Infrastructure Economic Development Bank, Revenue Bonds, Kaiser Hospital Assistance    8/11 at 102.00    A+    2,084,720 
     LLC, Series 2001A, 5.550%, 8/01/31             
1,500    California Statewide Community Development Authority, Hospital Revenue Bonds, Monterey    6/13 at 100.00    AAA    1,580,250 
     Peninsula Hospital, Series 2003B, 5.250%, 6/01/18 – FSA Insured             
1,500    California Statewide Community Development Authority, Insured Mortgage Hospital Revenue Bonds,    11/09 at 102.00    A    1,548,435 
     Mission Community Hospital, Series 2001, 5.375%, 11/01/26             
1,625    California Statewide Community Development Authority, Revenue Bonds, Kaiser Permanante System,    3/16 at 100.00    A+    1,633,970 
     Series 2006, 5.000%, 3/01/41             
545    California Statewide Community Development Authority, Revenue Bonds, Kaiser Permanente System,    8/16 at 100.00    A+    562,871 
     Series 2001C, 5.250%, 8/01/31             
1,880    California Statewide Community Development Authority, Revenue Bonds, Los Angeles Orthopaedic    12/07 at 101.00    AAA    1,901,188 
     Hospital Foundation, Series 2000, 5.500%, 6/01/17 – AMBAC Insured             
12,270    Total Health Care            12,613,425 
    Housing/Multifamily – 0.9%             
750    California Statewide Community Development Authority, Student Housing Revenue Bonds, EAH –    8/12 at 100.00    A    781,665 
     Irvine East Campus Apartments, LLC Project, Series 2002A, 5.500%, 8/01/22 – ACA Insured             
    Housing/Single Family – 0.1%             
145    California Housing Finance Agency, Home Mortgage Revenue Bonds, Series 2006H, 5.750%, 8/01/30 –    2/16 at 100.00    AAA    153,153 
     FGIC Insured (Alternative Minimum Tax)             
    Industrials – 2.0%             
1,250    California Pollution Control Financing Authority, Solid Waste Disposal Revenue Bonds, Republic    12/17 at 100.00    BBB+    1,298,775 
     Services Inc., Series 2002C, 5.250%, 6/01/23 (Mandatory put 12/01/17) (Alternative Minimum Tax)             
500    California Pollution Control Financing Authority, Solid Waste Disposal Revenue Bonds, Waste    1/16 at 102.00    BBB    501,415 
     Management Inc., Series 2002A, 5.000%, 1/01/22 (Alternative Minimum Tax)             
1,750    Total Industrials            1,800,190 
    Long-Term Care – 1.7%             
1,500    ABAG Finance Authority for Non-Profit Corporations, California, Insured Senior Living Revenue    11/12 at 100.00    A    1,543,155 
     Bonds, Odd Fellows Home of California, Series 2003A, 5.200%, 11/15/22             
    Tax Obligation/General – 22.4%             
500    California, General Obligation Bonds, Series 2003, 5.250%, 11/01/19 – RAAI Insured    11/13 at 100.00    AA    528,070 
    California, General Obligation Bonds, Series 2004:             
750     5.000%, 2/01/23    2/14 at 100.00    A+    776,550 
800     5.125%, 4/01/25    4/14 at 100.00    A+    833,760 
1,000    Fremont Unified School District, Alameda County, California, General Obligation Bonds, Series    8/12 at 101.00    AAA    1,041,730 
     2002A, 5.000%, 8/01/21 – FGIC Insured             
    Golden West Schools Financing Authority, California, General Obligation Revenue Refunding             
    Bonds, School District Program, Series 1999A:             
4,650     0.000%, 8/01/16 – MBIA Insured    No Opt. Call    AAA    3,151,491 
1,750     0.000%, 2/01/17 – MBIA Insured    No Opt. Call    AAA    1,153,880 
2,375     0.000%, 8/01/17 – MBIA Insured    No Opt. Call    AAA    1,531,566 
2,345     0.000%, 2/01/18 – MBIA Insured    No Opt. Call    AAA    1,468,251 
    Mountain View-Los Altos Union High School District, Santa Clara County, California, General             
    Obligation Capital Appreciation Bonds, Series 1995C:             
1,015     0.000%, 5/01/17 – MBIA Insured    No Opt. Call    AAA    661,892 
1,080     0.000%, 5/01/18 – MBIA Insured    No Opt. Call    AAA    668,628 
100    Roseville Joint Union High School District, Placer County, California, General Obligation    8/15 at 100.00    AAA    103,801 
     Bonds, Series 2006B, 5.000%, 8/01/27 – FGIC Insured             
3,220    Sacramento City Unified School District, Sacramento County, California, General Obligation    7/15 at 100.00    Aaa    3,341,458 
     Bonds, Series 2005, 5.000%, 7/01/27 – MBIA Insured             
1,500    San Diego Unified School District, San Diego County, California, General Obligation Bonds,    7/13 at 101.00    AAA    1,605,660 
     Series 2003E, 5.250%, 7/01/24 – FSA Insured             
768    San Diego Unified School District, San Diego County, California, General Obligation Bonds,    7/16 at 101.00    AAA    745,536 
     Series 2006F-1, 4.500%, 7/01/29 – FSA Insured (UB)             
2,565    Sunnyvale School District, Santa Clara County, California, General Obligation Bonds, Series    9/15 at 100.00    AAA    2,666,856 
     2005A, 5.000%, 9/01/26 – FSA Insured             
24,418    Total Tax Obligation/General            20,279,129 
    Tax Obligation/Limited – 19.2%             
1,000    Bell Community Redevelopment Agency, California, Tax Allocation Bonds, Bell Project Area,    10/13 at 100.00    AA    1,063,190 
     Series 2003, 5.625%, 10/01/33 – RAAI Insured             
3,500    California State Public Works Board, Lease Revenue Bonds, Department of Corrections,    No Opt. Call    AAA    4,028,988 
     Calipatria State Prison, Series 1991A, 6.500%, 9/01/17 – MBIA Insured             
1,000    California State Public Works Board, Lease Revenue Bonds, Department of Mental Health,    6/14 at 100.00    A    1,078,910 
     Coalinga State Hospital, Series 2004A, 5.500%, 6/01/23             
660    California, Economic Recovery Revenue Bonds, Series 2004A, 5.000%, 7/01/15    7/14 at 100.00    AA+    698,115 
120    Capistrano Unified School District, Orange County, California, Special Tax Bonds, Community    9/15 at 100.00    AAA    124,681 
     Facilities District, Series 2005, 5.000%, 9/01/24 – FGIC Insured             
360    Chino Redevelopment Agency, California, Merged Chino Redevelopment Project Area Tax Allocation    9/16 at 101.00    AAA    373,500 
     Bonds, Series 2006, 5.000%, 9/01/38 – AMBAC Insured (UB)             
1,000    Fontana Public Financing Authority, California, Tax Allocation Revenue Bonds, North Fontana    10/15 at 100.00    AAA    1,025,630 
     Redevelopment Project, Series 2005A, 5.000%, 10/01/32 – AMBAC Insured             
1,050    Golden State Tobacco Securitization Corporation, California, Enhanced Asset Backed Settlement    6/15 at 100.00    AAA    1,135,922 
     Revenue Bonds, Series 2005A, Residual Series 1503, 7.027%, 6/01/38 – FGIC Insured (IF)             
    Irvine, California, Unified School District, Community Facilities District Special Tax Bonds,             
    Series 2006A:             
60     5.000%, 9/01/26    9/16 at 100.00    N/R    59,303 
135     5.125%, 9/01/36    9/16 at 100.00    N/R    135,088 
215    Los Angeles Community Redevelopment Agency, California, Lease Revenue Bonds, Manchester    9/15 at 100.00    Aaa    219,982 
     Social Services Project, Series 2005, 5.000%, 9/01/37 – AMBAC Insured             
1,300    Orange County, California, Special Tax Bonds, Community Facilities District 03-1 of Ladera    8/12 at 101.00    N/R    1,367,899 
     Ranch, Series 2004A, 5.625%, 8/15/34             
105    Rialto Redevelopment Agency, California, Tax Allocation Bonds, Merged Project Area, Series    9/15 at 100.00    AAA    107,433 
     2005A, 5.000%, 9/01/35 – XLCA Insured             
130    Roseville, California, Certificates of Participation, Public Facilities, Series 2003A, 5.000%,    8/13 at 100.00    AAA    133,458 
     8/01/25 – AMBAC Insured             
605    Sacramento City Financing Authority, California, Lease Revenue Refunding Bonds, Series 1993A,    No Opt. Call    AAA    668,870 
     5.400%, 11/01/20 – MBIA Insured             
3,000    San Mateo County Transit District, California, Sales Tax Revenue Bonds, Series 2005A, 5.000%,    6/15 at 100.00    AAA    3,150,330 
     6/01/21 – MBIA Insured             
1,000    Santa Clara County Board of Education, California, Certificates of Participation, Series 2002,    4/12 at 101.00    AAA    1,027,590 
     5.000%, 4/01/25 – MBIA Insured             
1,000    Travis Unified School District, Solano County, California, Certificates of Participation,    9/16 at 100.00    Aaa    1,034,510 
     Series 2006, 5.000%, 9/01/26 – FGIC Insured             
16,240    Total Tax Obligation/Limited            17,433,399 
    Transportation – 6.5%             
1,150    Foothill/Eastern Transportation Corridor Agency, California, Toll Road Revenue Bonds, Series    1/10 at 100.00    BBB–    1,165,732 
     1995A, 5.000%, 1/01/35             
3,500    Los Angeles Harbors Department, California, Revenue Refunding Bonds, Series 2001B, 5.500%,    8/11 at 100.00    AAA    3,685,290 
     8/01/17 – AMBAC Insured (Alternative Minimum Tax)             
1,000    Port of Oakland, California, Revenue Bonds, Series 2002M, 5.250%, 11/01/20 – FGIC Insured    11/12 at 100.00    AAA    1,053,850 
5,650    Total Transportation            5,904,872 
    U.S. Guaranteed – 14.3% (3)             
400    Beverly Hills Unified School District, Los Angeles County, California, General Obligation Bonds,    8/12 at 100.00    AA (3)    420,588 
     Series 2002A, 5.000%, 8/01/26 (Pre-refunded 8/01/12)             
    California Department of Water Resources, Power Supply Revenue Bonds, Series 2002A:             
2,000     5.750%, 5/01/17 (Pre-refunded 5/01/12)    5/12 at 101.00    Aaa    2,180,520 
2,000     5.125%, 5/01/19 (Pre-refunded 5/01/12)    5/12 at 101.00    Aaa    2,125,860 
750    California Educational Facilities Authority, Revenue Bonds, Pepperdine University, Series 2002A,    8/09 at 100.00    N/R (3)    775,875 
     5.500%, 8/01/32 (Pre-refunded 8/01/09)             
2,600    California Educational Facilities Authority, Revenue Bonds, University of the Pacific, Series 2002,    11/11 at 100.00    A2 (3)    2,737,124 
     5.250%, 11/01/21 (Pre-refunded 11/01/11)             
1,000    California, General Obligation Bonds, Series 2004, 5.125%, 2/01/27 (Pre-refunded 2/01/14)    2/14 at 100.00    A+ (3)    1,067,250 
1,400    Golden State Tobacco Securitization Corporation, California, Enhanced Tobacco Settlement    6/13 at 100.00    AAA    1,512,392 
     Asset-Backed Bonds, Series 2003B, 5.500%, 6/01/33 (Pre-refunded 6/01/13)             
2,000    North Orange County Community College District, California, General Obligation Bonds, Series    8/12 at 101.00    AAA    2,115,600 
     2002A, 5.000%, 8/01/22 (Pre-refunded 8/01/12) – MBIA Insured             
12,150    Total U.S. Guaranteed            12,935,209 
    Utilities – 1.9%             
200    Los Angeles Department of Water and Power, California, Power System Revenue Bonds, Series    7/13 at 100.00    AAA    208,254 
     2003A-2, 5.000%, 7/01/21 – MBIA Insured             
215    Merced Irrigation District, California, Electric System Revenue Bonds, Series 2005, 5.125%,    9/15 at 100.00    AAA    222,381 
     9/01/31 – XLCA Insured             
1,225    Turlock Irrigation District, California, Revenue Refunding Bonds, Series 1992A, 6.250%,    No Opt. Call    Aaa    1,293,061 
     1/01/12 – MBIA Insured             
1,640    Total Utilities            1,723,696 
    Water and Sewer – 2.5%             
150    Healdsburg Public Financing Authority, California, Wastewater Revenue Bonds, Series 2006,    4/16 at 100.00    AAA    154,437 
     5.000%, 4/01/36 – MBIA Insured             
250    Sacramento County Sanitation District Financing Authority, California, Revenue Bonds, Series    6/16 at 100.00    AAA    259,933 
     2006, 5.000%, 12/01/31 – FGIC Insured             
825    South Feather Water and Power Agency, California, Water Revenue Certificates of Participation,    4/13 at 100.00    BBB    853,578 
     Solar Photovoltaic Project, Series 2003, 5.375%, 4/01/24             
1,000    Woodbridge Irrigation District, California, Certificates of Participation, Water Systems    7/13 at 100.00    BBB+    1,037,321 
     Project, Series 2003, 5.625%, 7/01/43             
2,225    Total Water and Sewer            2,305,269 
$        93,633    Total Long-Term Investments (cost $88,343,091) – 101.1%            91,690,959 
    Short-Term Investments – 1.3%             
$          1,150    Puerto Rico Government Development Bank, Adjustable Refunding Bonds, Variable Rate Demand        VMIG-1    1,150,000 
     Obligations, Series 1985, 3.570%, 12/01/15 – MBIA Insured (4)             
    Total Short-Term Investments (cost $1,150,000)            1,150,000 
    Total Investments (cost $89,493,091) – 102.4%            92,840,959 
    Floating Rate Obligations – (2.7)%            (2,458,000) 
    Other Assets Less Liabilities – 0.3%            247,063 
    Net Assets – 100%           $   90,630,022 

    The Fund may invest in “zero coupon” securities. A zero coupon security does not pay a regular interest 
    coupon to its holders during the life of the security. Tax-exempt income to the holder of the security comes 
    from accretion of the difference between the original purchase price of the security at issuance and the 
    par value of the security at maturity and is effectively paid at maturity. Such securities are included in the 
    portfolio with a 0.00% coupon rate in their description. The market prices of zero coupon securities 
    generally are more volatile than the market prices of securities that pay interest periodically. 
(1)    Optional Call Provisions: Dates (month and year) and prices of the earliest optional call or redemption. 
    There may be other call provisions at varying prices at later dates. Certain mortgage-backed securities 
    may be subject to periodic principal paydowns. 
(2)    Ratings: Using the higher of Standard & Poor’s or Moody’s rating. Ratings below BBB by Standard & Poor’s 
    Group or Baa by Moody’s Investor Service, Inc. are considered to be below investment grade. 
(3)    Backed by an escrow or trust containing sufficient U.S. Government or U.S. Government agency securities 
    which ensure the timely payment of principal and interest. Such investments are normally considered to be 
    equivalent to AAA rated securities. 
(4)    Investment has a maturity of greater than one year, but has variable rate and demand features which qualify 
    it as a short-term investment. The rate disclosed is that in effect at the end of the reporting period. This rate 
    changes periodically based on market conditions or a specified market index. 
N/R    Not rated. 
WI/DD    Purchased on a when-issued or delayed delivery basis. 
(IF)    Inverse floating rate investment. 
(UB)    Underlying bond of an inverse floating rate trust reflected as a financing transaction pursuant to the 
    provisions of SFAS No. 140. 

Income Tax Information

The following information is presented on an income tax basis. Differences between amounts for financial statement and federal income tax purposes are primarily due to the treatment of paydown gains and losses, timing differences in recognizing taxable market discount, timing differences in recognizing certain gains and losses on investment transactions and the treatment of investments in inverse floating rate transactions subject to SFAS No. 140.

At June 30, 2007, the cost of investments was $87,036,848.

Gross unrealized appreciation and gross unrealized depreciation of investments at June 30, 2007, were as follows:

Gross unrealized:     
  Appreciation    $3,420,989 
  Depreciation    (71,429) 
Net unrealized appreciation (depreciation) of investments    $3,349,560 

Item 2. Controls and Procedures.

  1. The registrant's principal executive and principal financial officers, or persons performing similar functions, have concluded that the registrant's disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the "1940 Act") (17 CFR 270.30a-3(c))) are effective, as of a date within 90 days of the filing date of this report that includes the disclosure required by this paragraph, based on their evaluation of the controls and procedures required by Rule 30a-3(b) under the 1940 Act (17 CFR 270.30a-3(b)) and Rule 13a-15(b) or 15d-15(b) under the Securities Exchange Act of 1934 (17 CFR 240.13a-15(b) or 240.15d-15(b)).
  2. There were no changes in the registrant's internal control over financial reporting (as defined in Rule 30a-3(d) under the 1940 Act (17 CFR 270.30a-3(d)) that occurred during the registrant's last fiscal quarter that have materially affected, or are reasonably likely to materially affect, the registrant's internal control over financial reporting.

Item 3. Exhibits.

File as exhibits as part of this Form a separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the 1940 Act (17 CFR 270.30a-2(a)), exactly as set forth below: EX-99 CERT Attached hereto.


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant)         Nuveen California Select Tax-Free Income Portfolio        

By (Signature and Title)*          /s/ Kevin J. McCarthy                    
                                                    Kevin J. McCarthy
                                                    Vice President and Secretary

Date         August 29, 2007        

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)*         /s/ Gifford R. Zimmerman                    
                                                   Gifford R. Zimmerman
                                                   Chief Administrative Officer (principal executive officer) 

Date         August 29, 2007        

By (Signature and Title)*         /s/ Stephen D. Foy                              
                                                   Stephen D. Foy
                                                   Vice President and Controller (principal financial officer) 

Date        August 29, 2007        

* Print the name and title of each signing officer under his or her signature.