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:            3/31          

Date of reporting period:          12/31/05         

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, 2005

Principal    Optional Call     
Amount (000)  Description  Provisions(1)  Ratings(2)  Value 
  Consumer Staples - 2.1%       
$ 235  California County Tobacco Securitization Agency, Tobacco Settlement Asset-Backed Bonds, Sonoma County   6/15 at 100.00  BBB  $ 227,621 
  Tobacco Securitization Corporation, Series 2005, 4.250%, 6/01/21       
1,675  California County Tobacco Securitization Agency, Tobacco Settlement Asset-Backed Revenue Bonds,   6/12 at 100.00  BBB  1,694,313 
  Fresno County Tobacco Funding Corporation, Series 2002, 5.625%, 6/01/23       
1,910  Total Consumer Staples      1,921,934 
  Education and Civic Organizations - 12.2%       
1,000  California Educational Facilities Authority, Revenue Bonds, Stanford University, Series 1999P, 5.000%, 12/01/23  12/09 at 101.00  AAA  1,055,430 
1,000  California Educational Facilities Authority, Revenue Bonds, University of San Diego, Series 2002A, 5.500%,  10/12 at 100.00  A2  1,058,800 
  10/01/32       
2,600  California Educational Facilities Authority, Revenue Bonds, University of the Pacific, Series 2002, 5.250%,  11/11 at 100.00  A2  2,722,720 
  11/01/21       
3,000  California Infrastructure Economic Development Bank, Revenue Bonds, J. David Gladstone Institutes,  10/11 at 101.00  A-  3,191,610 
  Series 2001, 5.500%, 10/01/1       
2,000  California State Public Works Board, Lease Revenue Bonds, University of California System, Series 2002A,  10/12 at 100.00  AAA  2,092,500 
  5.000%, 10/01/22 - FSA Insured       
1,000  Long Beach Bond Financing Authority, California, Lease Revenue Refunding Bonds, Long Beach Aquarium  11/11 at 101.00  AAA  1,056,600 
  of the South Pacific, Series 2001, 5.250%, 11/01/30 - AMBAC Insured       
10,600  Total Education and Civic Organizations      11,177,660 
  Health Care - 9.1%       
225  California Health Facilities Financing Authority, Revenue Bonds, Cedars-Sinai Medical Center, Series 2005,  11/15 at 100.00  A3  229,257 
  5.000%, 11/15/34       
2,000  California Infrastructure Economic Development Bank, Revenue Bonds, Kaiser Hospital Assistance LLC,   8/11 at 102.00  A+  2,118,600 
  Series 2001A, 5.550%, 8/01/31       
1,500  California Statewide Community Development Authority, Hospital Revenue Bonds, Monterey Peninsula Hospital,   6/13 at 100.00  AAA  1,611,825 
  Series 2003B, 5.250%, 6/01/18 - FSA Insured       
1,500  California Statewide Community Development Authority, Insured Mortgage Hospital Revenue Bonds, Mission  11/09 at 102.00  A  1,576,830 
  Community Hospital, Series 2001, 5.375%, 11/01/26       
90  California Statewide Community Development Authority, Revenue Bonds, Daughters of Charity Health System,   7/15 at 100.00  BBB+  93,236 
  Series 2005A, 5.250%, 7/01/24       
1,880  California Statewide Community Development Authority, Revenue Bonds, Los Angeles Orthopaedic Hospital   6/07 at 101.00  AAA  1,953,809 
  Foundation, Series 2000, 5.500%, 6/01/17 - AMBAC Insured       
790  Central California Joint Powers Health Finance Authority, Certificates of Participation, Community Hospitals of   2/06 at 100.00  Baa2  790,032 
  Central California, Series 1993, 5.000%, 2/01/23       
7,985  Total Health Care      8,373,589 
  Housing/Multifamily - 0.9%       
750  California Statewide Community Development Authority, Student Housing Revenue Bonds, EAH - Irvine East   8/12 at 100.00  A  792,968 
  Campus Apartments, LLC Project, Series 2002A, 5.500%, 8/01/22 - ACA Insured       
  Industrials - 1.4%       
1,250  California Pollution Control Financing Authority, Solid Waste Disposal Revenue Bonds, Republic Services Inc.,  6/23 at 100.00  BBB+  1,320,925 
  Series 2002C, 5.250%, 6/01/23 (Mandatory put 12/01/17) (Alternative Minimum Tax)       
  Long-Term Care - 1.7%       
1,500  ABAG Finance Authority for Non-Profit Corporations, California, Insured Senior Living Revenue Bonds,  11/12 at 100.00  A  1,573,260 
  Odd Fellows Home of California, Series 2003A, 5.200%, 11/15/22       
  Tax Obligation/General - 22.1%       
  California, General Obligation Bonds, Series 2003:       
500  5.250%, 11/01/19 - RAAI Insured  11/13 at 100.00  AA  543,835 
1,450  5.250%, 2/01/21  8/13 at 100.00  A  1,561,838 
1,000  5.250%, 2/01/22 - CIFG Insured  8/13 at 100.00  AAA  1,068,580 
  California, General Obligation Bonds, Series 2004:       
750  5.000%, 2/01/23  2/14 at 100.00  A  786,293 
800  5.125%, 4/01/25  4/14 at 100.00  A  845,104 
2,000  Fremont Unified School District, Alameda County, California, General Obligation Bonds, Series 2002A,  8/12 at 101.00  AAA  2,125,240 
  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  2,955,261 
1,750  0.000%, 2/01/17 - MBIA Insured  No Opt. Call  AAA  1,082,270 
2,375  0.000%, 8/01/17 - MBIA Insured  No Opt. Call  AAA  1,435,688 
2,345  0.000%, 2/01/18 - MBIA Insured  No Opt. Call  AAA  1,380,713 
395  Los Angeles Community College District, Los Angeles County, California, General Obligation Bonds,  8/15 at 100.00  AAA  417,953 
  Series 2005A, 5.000%, 6/01/26 - FSA Insured       
  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  620,612 
1,080  0.000%, 5/01/18 - MBIA Insured  No Opt. Call  AAA  628,808 
  Oakland Unified School District, Alameda County, California, General Obligation Bonds, Series 2005:       
130  5.000%, 8/01/25 - MBIA Insured  8/15 at 100.00  AAA  137,240 
135  5.000%, 8/01/26 - MBIA Insured  8/15 at 100.00  AAA  142,409 
1,500  San Diego Unified School District, San Diego County, California, General Obligation Bonds,  7/13 at 101.00  AAA  1,650,585 
  Series 2003E, 5.250%, 7/01/24 - FSA Insured       
  San Jose-Evergreen Community College District, Santa Clara County, California, General Obligation Bonds,       
  Series 2005A:       
100  5.000%, 9/01/25 - MBIA Insured  9/15 at 100.00  AAA  105,931 
150  5.000%, 9/01/27 - MBIA Insured  9/15 at 100.00  AAA  158,531 
2,565  Sunnyvale School District, Santa Clara County, California, General Obligation Bonds,  9/15 at 100.00  AAA  2,715,052 
  Series 2005A, 5.000%, 9/01/26 - FSA Insured       
24,690  Total Tax Obligation/General      20,361,943 
  Tax Obligation/Limited - 16.8%       
1,000  Bell Community Redevelopment Agency, California, Tax Allocation Bonds, Bell Project Area,  10/13 at 100.00  AA  1,068,150 
  Series 2003, 5.625%, 10/01/33 - RAAI Insured       
3,500  California State Public Works Board, Lease Revenue Bonds, Department of Corrections, Calipatria State Prison,  No Opt. Call  AAA  4,195,485 
  Series 1991A, 6.500%, 9/01/17 - MBIA Insured       
1,000  California State Public Works Board, Lease Revenue Bonds, Department of Mental Health, Coalinga State  6/14 at 100.00  A-  1,082,140 
  Hospital, Series 2004A, 5.500%, 6/01/23       
1,250  California, Economic Recovery Revenue Bonds, Series 2004A, 5.000%, 7/01/15  7/14 at 100.00  AA-  1,354,813 
1,000  Fontana Public Financing Authority, California, Tax Allocation Revenue Bonds, North Fontana Redevelopment  10/15 at 100.00  AAA  1,043,870 
  Project, Series 2005A, 5.000%, 10/01/32 - AMBAC Insured      
90  Hesperia Community Redevelopment Agency, California, Tax Allocation Bonds, Series 2005A, 5.000%, 9/15 at 100.00  AAA   95,558 
  9/01/20 - XLCA Insured      
1,300  Orange County, California, Special Tax Bonds, Community Facilities District 03-1 of Ladera Ranch, 8/12 at 101.00  N/R   1,337,206 
  Series 2004A, 5.625%, 8/15/34      
105  Rialto Redevelopment Agency, California, Tax Allocation Bonds, Merged Project Area, Series 2005A, 5.000%, 9/15 at 100.00  AAA   108,532 
  9/01/35 - XLCA Insured      
215  Riverside County Public Financing Authority, California, Tax Allocation Bonds, Multiple Projects, Series 2005A, 10/15 at 100.00  AAA   222,280 
  5.000%, 0/01/35 - XLCA Insured      
605  Sacramento City Financing Authority, California, Lease Revenue Refunding Bonds, Series 1993A, 5.400%, No Opt. Call  AAA   682,089 
  11/01/20 - MBIA Insured      
3,000  San Mateo County Transit District, California, Sales Tax Revenue Bonds, Series 2005A, 5.000%, 6/01/21 - 6/15 at 100.00  AAA   3,207,900 
  MBIA Insured      
1,000  Santa Clara County Board of Education, California, Certificates of Participation, Series 2002, 5.000%, 4/12 at 101.00  AAA   1,041,450 
  4/01/25 - MBIA Insured      
14,065  Total Tax Obligation/Limited     15,439,473 
  Transportation - 11.4%      
1,150  Foothill/Eastern Transportation Corridor Agency, California, Toll Road Revenue Bonds, Series 1995A, 1/10 at 100.00  BBB-   1,093,466 
  5.000%, 1/01/35      
5,000  Los Angeles Harbors Department, California, Revenue Refunding Bonds, Series 2001B, 5.500%, 8/01/17 - 8/11 at 100.00  AAA   5,352,547 
  AMBAC Insured (Alternative Minimum Tax)      
2,915  Palm Springs Financing Authority, California, Palm Springs Regional Airport Revenue Bonds, Series 1992, 1/06 at 100.00  AAA   2,920,830 
  6.000%, 1/01/12 - MBIA 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   1,077,780 
10,065  Total Transportation     10,444,623 
  U.S. Guaranteed(3) - 10.4%      
500  Beverly Hills Unified School District, Los Angeles County, California, General Obligation Bonds, Series 2002A, 8/12 at 100.00   AA(3)   541,465 
  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  A2(3)   2,262,620 
2,000  5.125%, 5/01/19 (Pre-refunded 5/01/12) 5/12 at 101.00  A2(3)   2,192,280 
750  California Educational Facilities Authority, Revenue Bonds, Pepperdine University, Series 2002A, 5.500%, 8/09 at 100.00  A1(3)   805,927 
  8/01/32 (Pre-refunded 8/01/09)      
1,400  Golden State Tobacco Securitization Corporation, California, Enhanced Tobacco Settlement Asset-Backed 6/13 at 100.00  Aaa   1,558,116 
  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 2002A, 8/12 at 101.00  AAA   2,170,660 
  5.000%, 8/01/22 (Pre-refunded 8/01/12) - MBIA Insured      
8,650  Total U.S. Guaranteed     9,531,068 
  Utilities - 2.0%      
200  Los Angeles Department of Water and Power, California, Power System Revenue Bonds, Series 2003A-2, 7/13 at 100.00  AAA   212,494 
  5.000%, 7/01/21 - MBIA Insured      
215  Merced Irrigation District, California, Electric System Revenue Bonds, Series 2005, 5.125%, 9/01/31 - 9/15 at 100.00  AAA   225,170 
  XLCA Insured      
1,225  Turlock Irrigation District, California, Revenue Refunding Bonds, Series 1992A, 6.250%, 1/01/12 - MBIA Insured No Opt. Call  AAA   1,359,701 
1,640  Total Utilities     1,797,365 
  Water and Sewer - 7.8%       
2,160  California Statewide Community Development Authority, Water and Wastewater Revenue Bonds, Pooled  10/11 at 101.00  AAA  2,308,651 
  Financing Program, Series 2001B, 5.125%, 10/01/22 - FSA Insured       
2,800  Los Angeles, California, Wastewater System Revenue Bonds, Series 1998A, 5.000%, 6/01/23 - FGIC Insured  6/08 at 101.00  AAA  2,920,288 
825  South Feather Water and Power Agency, California, Water Revenue Certificates of Participation, Solar  4/13 at 100.00  BBB  849,882 
  Photovoltaic Project, Series 2003, 5.375%, 4/01/24       
1,000  Woodbridge Irrigation District, California, Certificates of Participation, Water Systems Project, Series 2003,  7/13 at 100.00  BBB+  1,046,910 
  5.625%, 7/01/43       
6,785  Total Water and Sewer      7,125,731 
$ 89,890  Total Investments (cost $85,094,962) - 97.9%      89,860,539 
  Other Assets Less Liabilities - 2.1%      1,961,733 
  Net Assets - 100%      $ 91,822,272 
 

(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 Baa by Moody’s Investor 
  Service, Inc. or BBB by Standard & Poor’s Group are considered to be below investment grade. 
(3 )  Securities are backed by an escrow or trust containing sufficient U.S. Government or U.S. Government 
  agency securities which ensures the timely payment of principal and interest. Such securities are normally 
  considered to be equivalent to AAA rated securities. 
N/R   Investment is not rated. 

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 timing differences in recognizing taxable market discount and timing differences in recognizing certain gains and losses on investment transactions.

At December 31, 2005, the cost of investments was $85,093,904.

Gross unrealized appreciation and gross unrealized depreciation of investments at December 31, 2005, were as follows:

Gross unrealized:   
    Appreciation  $ 4,785,925  
    Depreciation  (19,290 ) 
Net unrealized appreciation (depreciation) of investments  $ 4,766,635  

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         2/27/06        

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         2/27/06        

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

Date         2/27/06        

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