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)


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


Jessica R. Droeger—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:            03/31          

Date of reporting period:         12/31/06         

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)             
    December 31, 2006             
Principal        Optional Call         
Amount (000)    Description    Provisions (1)    Ratings (2)    Value 
    Consumer Staples – 2.0%             
$             235    California County Tobacco Securitization Agency, Tobacco Settlement Asset-Backed Bonds, Sonoma    6/15 at 100.00    BBB   $   228,639 
     County Tobacco Securitization Corporation, Series 2005, 4.250%, 6/01/21             
1,620    California County Tobacco Securitization Agency, Tobacco Settlement Asset-Backed Revenue    6/12 at 100.00    BBB    1,638,598 
     Bonds, Fresno County Tobacco Funding Corporation, Series 2002, 5.625%, 6/01/23             
1,855    Total Consumer Staples            1,867,237 
    Education and Civic Organizations – 9.3%             
1,000    California Educational Facilities Authority, Revenue Bonds, Stanford University, Series 1999P,    12/09 at 101.00    AAA    1,040,980 
     5.000%, 12/01/23             
45    California Educational Facilities Authority, Revenue Bonds, University of Redlands, Series    10/15 at 100.00    A3    46,759 
     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    1,072,920 
     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    37,220 
45     5.000%, 11/01/25    11/15 at 100.00    A2    47,582 
3,000    California Infrastructure Economic Development Bank, Revenue Bonds, J. David Gladstone    10/11 at 101.00    A–    3,200,969 
     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    2,100,220 
     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    1,060,210 
     Aquarium of the South Pacific, Series 2001, 5.250%, 11/01/30 – AMBAC Insured             
8,125    Total Education and Civic Organizations            8,606,860 
    Health Care – 11.4%             
335    California Health Facilities Financing Authority, Revenue Bonds, Cedars-Sinai Medical Center,    11/15 at 100.00    A3    348,524 
     Series 2005, 5.000%, 11/15/34             
2,000    California Infrastructure Economic Development Bank, Revenue Bonds, Kaiser Hospital Assistance    8/11 at 102.00    A+    2,126,540 
     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    1,618,530 
     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    1,573,275 
     Mission Community Hospital, Series 2001, 5.375%, 11/01/26             
1,515    California Statewide Community Development Authority, Revenue Bonds, Kaiser Permanante System,    3/16 at 100.00    A+    1,574,206 
     Series 2006, 5.000%, 3/01/41             
545    California Statewide Community Development Authority, Revenue Bonds, Kaiser Permanente System,    8/16 at 100.00    A+    582,000 
     Series 2001C, 5.250%, 8/01/31             
1,880    California Statewide Community Development Authority, Revenue Bonds, Los Angeles Orthopaedic    6/07 at 101.00    AAA    1,912,261 
     Hospital Foundation, Series 2000, 5.500%, 6/01/17 – AMBAC Insured             
775    Central California Joint Powers Health Finance Authority, Certificates of Participation,    2/07 at 100.00    Baa2    775,186 
     Community Hospitals of Central California, Series 1993, 5.000%, 2/01/23             
10,050    Total Health Care            10,510,522 
    Housing/Multifamily – 0.9%             
750    California Statewide Community Development Authority, Student Housing Revenue Bonds, EAH –    8/12 at 100.00    A    792,548 
     Irvine East Campus Apartments, LLC Project, Series 2002A, 5.500%, 8/01/22 – ACA Insured             
    Housing/Single Family – 0.2%             
145    California Housing Finance Agency, Home Mortgage Revenue Bonds, Series 2006H, 5.750%,    2/16 at 100.00    AAA    156,127 
     8/01/30 – FGIC Insured (Alternative Minimum Tax)             
    Industrials – 2.0%             
1,250    California Pollution Control Financing Authority, Solid Waste Disposal Revenue Bonds, Republic    No Opt. Call    BBB+    1,333,488 
     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    522,835 
     Management Inc., Series 2002A, 5.000%, 1/01/22 (Alternative Minimum Tax)             
1,750    Total Industrials            1,856,323 
    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    1,573,590 
     Bonds, Odd Fellows Home of California, Series 2003A, 5.200%, 11/15/22             
    Tax Obligation/General – 24.6%             
500    California, General Obligation Bonds, Series 2003, 5.250%, 11/01/19 – RAAI Insured    11/13 at 100.00    AA    542,650 
    California, General Obligation Bonds, Series 2004:             
750     5.000%, 2/01/23    2/14 at 100.00    A+    788,588 
800     5.125%, 4/01/25    4/14 at 100.00    A+    852,256 
1,000     5.125%, 2/01/27    2/14 at 100.00    A+    1,061,520 
2,000    Fremont Unified School District, Alameda County, California, General Obligation Bonds, Series    8/12 at 101.00    AAA    2,142,760 
     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    3,174,137 
1,750     0.000%, 2/01/17 – MBIA Insured    No Opt. Call    AAA    1,160,863 
2,375     0.000%, 8/01/17 – MBIA Insured    No Opt. Call    AAA    1,543,726 
2,345     0.000%, 2/01/18 – MBIA Insured    No Opt. Call    AAA    1,483,846 
    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    666,490 
1,080     0.000%, 5/01/18 – MBIA Insured    No Opt. Call    AAA    676,372 
100    Roseville Joint Union High School District, Placer County, California, General Obligation    8/15 at 100.00    AAA    106,494 
     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    3,427,528 
     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    1,643,790 
     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    775,219 
     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    2,736,727 
     2005A, 5.000%, 9/01/26 – FSA Insured             
26,418    Total Tax Obligation/General            22,782,966 
    Tax Obligation/Limited – 19.5%             
1,000    Bell Community Redevelopment Agency, California, Tax Allocation Bonds, Bell Project Area,    10/13 at 100.00    AA    1,088,200 
     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    4,152,574 
     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    1,103,920 
     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+    718,489 
120    Capistrano Unified School District, Orange County, California, Special Tax Bonds, Community    9/15 at 100.00    AAA    128,034 
     Facilities District, Series 2005, 5.000%, 9/01/24 – FGIC Insured             
360    Chino Redevelopment Agency, California, Merged Chino Project Area Tax Allocation Bonds, Series    9/16 at 101.00    AAA    384,545 
     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    1,057,670 
     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    1,219,113 
     Revenue Bonds, Series 2005A, Residual Series 1503, 6.806%, 6/01/38 – FGIC Insured (IF)             
90    Hesperia Community Redevelopment Agency, California, Tax Allocation Bonds, Series 2005A,    9/15 at 100.00    AAA    96,297 
     5.000%, 9/01/20 – XLCA Insured             
    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    60,339 
135     5.125%, 9/01/36    9/16 at 100.00    N/R    137,048 
215    Los Angeles Community Redevelopment Agency, California, Lease Revenue Bonds, Manchester Social    9/15 at 100.00    Aaa    226,343 
     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    1,356,069 
     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    110,540 
     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    136,423 
     8/01/25 – AMBAC Insured             
605    Sacramento City Financing Authority, California, Lease Revenue Refunding Bonds, Series 1993A,    No Opt. Call    AAA    687,746 
     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    3,227,069 
     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    1,049,440 
     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    1,064,220 
     Series 2006, 5.000%, 9/01/26 – FGIC Insured             
16,330    Total Tax Obligation/Limited            18,004,079 
    Transportation – 8.2%             
1,150    Foothill/Eastern Transportation Corridor Agency, California, Toll Road Revenue Bonds, Series    1/10 at 100.00    BBB–    1,153,462 
     1995A, 5.000%, 1/01/35             
5,000    Los Angeles Harbors Department, California, Revenue Refunding Bonds, Series 2001B, 5.500%,    8/11 at 100.00    AAA    5,325,399 
     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    1,078,220 
7,150    Total Transportation            7,557,081 
    U.S. Guaranteed – 15.1% (3)             
400    Beverly Hills Unified School District, Los Angeles County, California, General Obligation    8/12 at 100.00    AA (3)    429,472 
     Bonds, 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    2,230,300 
2,000     5.125%, 5/01/19 (Pre-refunded 5/01/12)    5/12 at 101.00    Aaa    2,169,980 
750    California Educational Facilities Authority, Revenue Bonds, Pepperdine University, Series    8/09 at 100.00    A1 (3)    787,080 
     2002A, 5.500%, 8/01/32 (Pre-refunded 8/01/09)             
2,600    California Educational Facilities Authority, Revenue Bonds, University of the Pacific, Series    11/11 at 100.00    A2 (3)    2,789,436 
     2002, 5.250%, 11/01/21 (Pre-refunded 11/01/11)             
1,400    Golden State Tobacco Securitization Corporation, California, Enhanced Tobacco Settlement    6/13 at 100.00    AAA    1,549,156 
     Asset-Backed Bonds, Series 2003B, 5.500%, 6/01/33 (Pre-refunded 6/01/13)             
1,800    Los Angeles, California, Wastewater System Revenue Bonds, Series 1998A, 5.000%, 6/01/23    6/08 at 101.00    AAA    1,855,872 
     (Pre-refunded 6/01/08) – FGIC Insured             
2,000    North Orange County Community College District, California, General Obligation Bonds, Series    8/12 at 101.00    AAA    2,159,560 
     2002A, 5.000%, 8/01/22 (Pre-refunded 8/01/12) – MBIA Insured             
12,950    Total U.S. Guaranteed            13,970,856 
    Utilities – 1.9%             
200    Los Angeles Department of Water and Power, California, Power System Revenue Bonds, Series    7/13 at 100.00    AAA    214,372 
     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    229,076 
     9/01/31 – XLCA Insured             
1,225    Turlock Irrigation District, California, Revenue Refunding Bonds, Series 1992A, 6.250%,    No Opt. Call    Aaa    1,317,794 
     1/01/12 – MBIA Insured             
1,640    Total Utilities            1,761,242 
    Water and Sewer – 2.5%             
150    Healdsburg Public Financing Authority, California, Wastewater Revenue Bonds, Series 2006,    4/16 at 100.00    AAA    159,530 
     5.000%, 4/01/36 – MBIA Insured             
250    Sacramento County Sanitation District Financing Authority, California, Revenue Bonds, Series    6/16 at 100.00    AAA    267,533 
     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    865,978 
     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+    1,052,190 
     Project, Series 2003, 5.625%, 7/01/43             
2,225    Total Water and Sewer        2,345,231 
$        90,888    Total Investments (cost $86,469,768) – 99.3%        91,784,662 
    Floating Rate Obligations – (0.8%)        (758,000) 
    Other Assets Less Liabilities – 1.5%        1,384,217 
    Net Assets – 100%           $  92,410,879 

(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. 
N/R    Not rated. 
(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 December 31, 2006, the cost of investments was $85,710,651.

Gross unrealized appreciation and gross unrealized depreciation of investments at December 31, 2006, were as follows:

Gross unrealized:     
  Appreciation    $5,316,323 
  Depreciation    — 
Net unrealized appreciation (depreciation) of investments    $5,316,323 

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/ Jessica R. Droeger                     
                                                    Jessica R. Droeger
                                                    Vice President and Secretary

Date         March 1, 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         March 1, 2007        

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

Date        March 1, 2007        

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