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         811-6548         

        Nuveen 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 Select Tax-Free Income Portfolio (NXP)
December 31, 2005

Principal    Optional Call   
Amount (000)  Description  Provisions(1)  Ratings(2) Value 
  Alaska - 1.1%     
$ 2,475  Alaska Municipal Bond Bank Authority, General Obligation Bonds, Series 2003E, 5.250%, 12/01/23 - MBIA Insured  12/13 at 100.00  AAA $ 2,697,181 
  California - 4.6%     
2,000  Alameda Corridor Transportation Authority, California, Subordinate Lien Revenue Bonds,  10/17 at 100.00  AAA 1,524,760 
  Series 2004A, 0.000%, 10/01/25 - AMBAC Insured     
3,325  California Department of Water Resources, Power Supply Revenue Bonds, Series 2002A, 6.000%, 5/01/14  5/12 at 101.00  A2 3,769,918 
200  Contra Costa County, California, Certificates of Participation Refunding, Merrithew Memorial Hospital  11/07 at 102.00  AAA 211,056 
  Replacement, Series 1997, 5.375%, 11/01/17 - MBIA Insured     
3,000  Golden State Tobacco Securitization Corporation, California, Tobacco Settlement Asset-Backed Bonds,  6/13 at 100.00  BBB 3,374,340 
  Series 2003A-1, 6.750%, 6/01/39     
1,130  Los Angeles Department of Water and Power, California, Waterworks Revenue Refunding Bonds,  7/11 at 100.00  AAA 1,164,860 
  Series 2001A, 5.125%, 7/01/41 - FGIC Insured     
365  Los Angeles, California, Parking System Revenue Bonds, Series 1999A, 5.250%, 5/01/29 - AMBAC Insured  5/09 at 101.00  AAA 384,743 
750  Tobacco Securitization Authority of Northern California, Tobacco Settlement Asset-Backed Bonds,  6/15 at 100.00  BBB 753,135 
  Series 2005A-1, 5.500%, 6/01/45     
10,770  Total California    11,182,812 
  Colorado - 13.4%     
Colorado Health Facilities Authority, Revenue Bonds, Catholic Health Initiatives, Series 2002A: 
1,700  5.500%, 3/01/22 (3)  3/12 at 100.00  AA(3) 1,854,581 
1,300  5.500%, 3/01/22  3/12 at 100.00  AA 1,397,149 
1,000  Colorado Water Resources and Power Development Authority, Small Water Resources Revenue Bonds,  11/10 at 100.00  AAA 1,094,240 
  Series 2000A, 5.800%, 11/01/20 - FGIC Insured     
10,750  Denver City and County, Colorado, Airport System Revenue Bonds, Series 1991D, 7.750%, 11/15/13  No Opt. Call  A 12,408,079 
  (Alternative Minimum Tax)     
640  Denver City and County, Colorado, Airport System Revenue Bonds, Series 1996A, 5.500%, 11/15/25 -  11/06 at 101.00  AAA 656,845 
  MBIA Insured     
230  Denver City and County, Colorado, Airport System Revenue Bonds, Series 1996D, 5.500%, 11/15/25 -  11/06 at 101.00  AAA 236,054 
  MBIA Insured     
5,000  Denver City and County, Colorado, Airport System Revenue Refunding Bonds,  11/11 at 100.00  AAA 5,376,700 
  Series 2001A, 5.625%, 11/15/17 - FGIC Insured (Alternative Minimum Tax)     
  Denver Convention Center Hotel Authority, Colorado, Senior Revenue Bonds, Convention Center Hotel,     
  Series 2003A:     
1,000  5.000%, 12/01/22 - XLCA Insured  12/13 at 100.00  AAA 1,050,300 
3,000  5.000%, 12/01/23 - XLCA Insured  12/13 at 100.00  AAA 3,144,720 
5,000  E-470 Public Highway Authority, Colorado, Senior Revenue Bonds, Series 2000B, 0.000%, 9/01/28  9/10 at 31.42  AAA 1,319,100 
  (Pre-refunded 9/01/10) - MBIA Insured (3)     
3,160  Northwest Parkway Public Highway Authority, Colorado, Revenue Bonds, Senior Series 2001A, 5.500%,  6/11 at 102.00  AAA 3,461,970 
  6/15/20 - AMBAC Insured     
32,780  Total Colorado    31,999,738 
  District of Columbia - 0.5%       
1,000  District of Columbia, Hospital Revenue Refunding Bonds, Medlantic Healthcare Group, Series 1996A,  8/06 at 102.00  AAA   1,035,350 
  5.750%, 8/15/16 - MBIA Insured       
265  District of Columbia, Revenue Bonds, Catholic University of America, Series 1999, 5.625%, 10/01/29 -  10/09 at 101.00  AAA   284,435 
  AMBAC Insured       
1,265  Total District of Columbia      1,319,785 
  Florida - 4.6%       
450  Escambia County, Florida, Pollution Control Revenue Bonds, Champion International Corporation,  6/06 at 100.00  BBB   450,500 
  Series 1993, 5.875%, 6/01/22 (Alternative Minimum Tax)       
10,000  JEA St. John's River Power Park System, Florida, Revenue Refunding Bonds, Issue 2, Series 2002-17,  10/11 at 100.00  Aa2   10,590,400 
  5.000%, 10/01/17       
10,450  Total Florida      11,040,900 
  Hawaii - 0.6%       
1,330  Hawaii, Certificates of Participation, Kapolei State Office Building, Series 1998A, 5.000%, 5/01/17 -  11/08 at 101.00  AAA   1,393,015 
  AMBAC Insured       
  Illinois - 14.1%       
  Chicago Heights, Illinois, General Obligation Corporate Purpose Bonds, Series 1993:       
3,820  5.650%, 12/01/15 - FGIC Insured  12/08 at 100.00  AAA   4,044,616 
2,600  5.650%, 12/01/17 - FGIC Insured  12/08 at 100.00  AAA   2,751,632 
2,500  Chicago, Illinois, Special Facility Revenue Refunding Bonds, O'Hare International Airport, United Air Lines Inc.  No Opt. Call  N/R   438,300 
  Project, Series 2001C, 6.300%, 5/01/16 (4)       
1,000  DuPage County Community School District 200, Wheaton, Illinois, General Obligation Bonds,  11/13 at 100.00  Aaa   1,087,530 
  Series 2003B, 5.250%, 11/01/20 - FSA Insured       
1,000  Illinois Educational Facilities Authority, Revenue Bonds, Midwestern University,  5/08 at 101.00  A   1,032,260 
  Series 1998B, 5.500%, 5/15/18 - ACA Insured       
600  Illinois Educational Facilities Authority, Student Housing Revenue Bonds, Educational Advancement Foundation  5/12 at 101.00  Baa3   649,998 
  Fund, University Center Project, Series 2002, 6.000%, 5/01/22       
4,000  Illinois Finance Authority, Revenue Bonds, Northwestern Memorial Hospital, Series 2004A, 5.500%, 8/15/43  8/14 at 100.00  AA+   4,274,240 
1,320  Illinois Health Facilities Authority, Revenue Bonds, Decatur Memorial Hospital, Series 2001, 5.600%, 10/01/16  10/11 at 100.00  A   1,402,394 
2,700  Illinois Health Facilities Authority, Revenue Bonds, Lake Forest Hospital, Series 2002A, 6.000%, 7/01/17  7/12 at 100.00  A-   2,946,780 
300  Illinois Health Facilities Authority, Revenue Bonds, Rush-Presbyterian St. Luke's Medical Center Obligated  5/06 at 100.00  AAA   300,381 
  Group, Series 1993, 5.250%, 11/15/20 - MBIA Insured       
2,275  Illinois Health Facilities Authority, Revenue Refunding Bonds, Elmhurst Memorial Healthcare,  1/13 at 100.00  A2   2,538,627 
  Series 2002, 6.250%, 1/01/17       
1,530  Illinois Health Facilities Authority, Revenue Refunding Bonds, Evangelical Hospitals Corporation,  No Opt. Call  N/R(3 )  1,591,185 
  Series 1992B, 6.500%, 4/15/09 (3)       
3,125  Metropolitan Pier and Exposition Authority, Illinois, Revenue Bonds, McCormick Place Expansion Project,  No Opt. Call  AAA   1,895,969 
  Series 1992A, 0.000%, 6/15/17 - FGIC Insured       
5,000  Metropolitan Pier and Exposition Authority, Illinois, Revenue Refunding Bonds, McCormick Place Expansion  6/12 at 101.00  AAA   5,265,550 
  Project, Series 2002B, 5.000%, 6/15/21 - MBIA Insured       
1,300  Schaumburg, Illinois, General Obligation Bonds, Series 2004B, 5.250%, 12/01/34 - FGIC Insured  12/14 at 100.00  AAA   1,392,131 
  Yorkville, Illinois, General Obligation Debt Certificates, Series 2003:       
1,000  5.000%, 12/15/19 - RAAI Insured  12/11 at 100.00  AA   1,030,070 
1,000  5.000%, 12/15/20 - RAAI Insured  12/11 at 100.00  AA   1,027,960 
35,070  Total Illinois      33,669,623 
  Indiana - 8.3%       
5,000  Duneland School Building Corporation, Indiana, First Mortgage Refunding Bonds, Series 1999,  2/09 at 101.00  AAA  5,266,200 
  5.125%, 2/01/18 - MBIA Insured       
1,000  Franklin Community Multi-School Building Corporation, Marion County, Indiana, First Mortgage Revenue  7/14 at 100.00  AAA  1,052,870 
  Bonds, Series 2004, 5.000%, 7/15/22 - FGIC Insured       
2,000  Indiana Health Facility Financing Authority, Hospital Revenue Refunding Bonds, Columbus Regional Hospital,  No Opt. Call  AAA  2,367,540 
  Series 1993, 7.000%, 8/15/15 - FSA Insured       
9,855  Indianapolis Local Public Improvement Bond Bank, Indiana, Waterworks Project, Series 2002A,  7/12 at 100.00  AAA  10,472,711 
  5.125%, 7/01/21 - MBIA Insured       
750  West Clark 2000 School Building Corporation, Clark County, Indiana, First Mortgage Bonds, Series 2005,  1/15 at 100.00  AAA  791,558 
  5.000%, 7/15/22 - MBIA Insured       
18,605  Total Indiana      19,950,879 
  Kansas - 0.3%       
750  Wamego, Kansas, Pollution Control Revenue Bonds, Kansas Gas and Electric Company, Series 2004,  6/14 at 100.00  AAA  802,538 
  5.300%, 6/01/31 - MBIA Insured       
  Kentucky - 0.5%       
1,100  Jefferson County, Kentucky, Health System Revenue Bonds, Alliant Health System Inc., Series 1998, 5.125%,  10/08 at 101.00  AAA  1,143,065 
  10/01/18 - MBIA Insured       
  Louisiana - 0.4%       
1,000  Tobacco Settlement Financing Corporation, Louisiana, Tobacco Settlement Asset-Backed Bonds,  5/11 at 101.00  BBB  1,044,150 
  Series 2001B, 5.875%, 5/15/39       
  Massachusetts - 0.4%       
500  Massachusetts Health and Educational Facilities Authority, Revenue Bonds, Partners HealthCare System Inc.,  7/11 at 101.00  AA-  551,805 
  Series 2001C, 6.000%, 7/01/17       
410  Massachusetts Turnpike Authority, Metropolitan Highway System Revenue Bonds, Subordinate Series 1999A,  1/09 at 101.00  AAA  415,752 
  5.000%, 1/01/39 - AMBAC Insured       
910  Total Massachusetts      967,557 
  Michigan - 1.7%       
1,000  Michigan State Hospital Finance Authority, Hospital Revenue Bonds, Detroit Medical Center Obligated Group,  8/08 at 101.00  BB-  969,220 
  Series 1998A, 5.125%, 8/15/18       
2,900  Michigan State Hospital Finance Authority, Hospital Revenue Refunding Bonds, Trinity Health Credit Group,  12/12 at 100.00  AA-  3,058,137 
  Series 2002C, 5.375%, 12/01/30       
3,900  Total Michigan      4,027,357 
  Minnesota - 0.1%       
345  Minnesota Housing Finance Agency, Single Family Mortgage Revenue Bonds, Series 1995A, 5.200%, 1/01/17  7/08 at 101.00  AA+  355,478 
  Mississippi - 1.6%       
3,600  Calhoun County, Mississippi, Solid Waste Disposal Revenue Bonds, Weyerhauser Company Project,  4/07 at 103.00  BBB  3,807,792 
  Series 1992, 6.875%, 4/01/16 (Alternative Minimum Tax)       
  Nevada - 6.7%       
2,500  Clark County, Nevada, Motor Vehicle Fuel Tax Highway Improvement Revenue Bonds, Series 2003,  7/13 at 100.00  AAA  2,644,225 
  5.000%, 7/01/23 - AMBAC Insured       
  Director of Nevada State Department of Business and Industry, Revenue Bonds, Las Vegas Monorail Project,       
  First Tier, Series 2000:       
2,360  0.000%, 1/01/21 - AMBAC Insured  No Opt. Call  AAA  1,165,203 
3,500  0.000%, 1/01/22 - AMBAC Insured  No Opt. Call  AAA  1,640,940 
6,025  5.375%, 1/01/40 - AMBAC Insured  1/10 at 100.00  AAA  6,314,983 
1,515  Reno, Nevada, Capital Improvement Revenue Bonds, Series 2002, 5.500%, 6/01/21 - FGIC Insured  6/12 at 100.00  AAA  1,647,850 
2,555  Reno, Nevada, Capital Improvement Revenue Bonds, Series 2002, 5.500%, 6/01/21 (Pre-refunded 6/01/12) -  6/12 at 100.00  AAA  2,830,659 
  FGIC Insured (3)       
18,455  Total Nevada      16,243,860 
  New Hampshire - 0.2%       
550  New Hampshire Housing Finance Agency, Single Family Mortgage Acquisition Bonds, Series 2001A,  5/11 at 100.00  Aa2  556,980 
  5.600%, 7/01/21 (Alternative Minimum Tax)       
  New Jersey - 1.9%       
2,500  New Jersey Health Care Facilities Financing Authority, Revenue Bonds, Somerset Medical Center, Series 2003,  7/13 at 100.00  Baa3  2,600,375 
  5.500%, 7/01/23       
1,820  Tobacco Settlement Financing Corporation, New Jersey, Tobacco Settlement Asset-Backed Bonds,  6/12 at 100.00  BBB  1,891,653 
  Series 2002, 5.750%, 6/01/32       
4,320  Total New Jersey      4,492,028 
  New Mexico - 1.7%       
4,000  University of New Mexico, FHA-Insured Mortgage Hospital Revenue Bonds, Series 2004, 4.625%, 7/01/25 -  7/14 at 100.00  AAA  4,020,960 
  FSA Insured       
  New York - 1.3%       
1,000  Dormitory Authority of the State of New York, FHA-Insured Mortgage Revenue Bonds, Kaleida Health,  2/14 at 100.00  AAA  1,046,250 
  Series 2004, 5.050%, 2/15/25       
1,600  Dormitory Authority of the State of New York, Revenue Bonds, Mount Sinai NYU Health Obligated Group,  7/10 at 101.00  Ba1  1,721,904 
  Series 2000A, 6.500%, 7/01/17       
450  Long Island Power Authority, New York, Electric System General Revenue Bonds, Series 1998A,  6/08 at 101.00  AAA  471,591 
  5.125%, 12/01/22 - FSA Insured       
3,050  Total New York      3,239,745 
  North Carolina - 1.4%       
500  Appalachian State University, North Carolina, Utilities System Revenue Refunding Bonds, Series 1998,  5/08 at 102.00  AAA  523,760 
  5.000%, 5/15/24 - MBIA Insured       
2,195  North Carolina Eastern Municipal Power Agency, Power System Revenue Refunding Bonds, Series 1993B,  1/06 at 100.00  BBB  2,216,248 
  5.500%, 1/01/21       
500  Raleigh Durham Airport Authority, North Carolina, Airport Revenue Bonds, Series 2001A, 5.250%, 11/01/17 -  5/11 at 101.00  Aaa  534,980 
  FGIC Insured       
3,195  Total North Carolina      3,274,988 
  Ohio - 0.6%       
300  Lebanon, Ohio, Electric System Mortgage Revenue Bonds, Series 2001, 5.500%, 12/01/17 - AMBAC Insured  12/10 at 101.00  AAA  327,216 
1,000  Ohio Housing Finance Agency, GNMA Mortgage-Backed Securities Program Residential Mortgage Remarketed  9/07 at 102.00  Aaa  1,039,090 
  Revenue Bonds, Series 1997A-1, 6.050%, 9/01/17 (Alternative Minimum Tax)       
1,300  Total Ohio      1,366,306 
  Oklahoma - 2.1%       
1,000  Norman Regional Hospital Authority, Oklahoma, Hospital Revenue Bonds, Series 2005, 5.375%, 9/01/36  9/16 at 100.00  BBB-  1,009,460 
4,000  Oklahoma Development Finance Authority, Revenue Bonds, St. John Health System, Series 2004,  2/14 at 100.00  AA  4,144,280 
  5.000%, 2/15/24       
5,000  Total Oklahoma      5,153,740 
  Pennsylvania - 0.8%       
500  Pennsylvania Higher Educational Facilities Authority, Revenue Bonds, Widener University, Series 2003,  7/13 at 100.00  BBB+  525,215 
  5.250%, 7/15/24       
700  Pennsylvania Turnpike Commission, Turnpike Revenue Bonds, Series 2004A, 5.500%, 12/01/31 - AMBAC  12/14 at 100.00  AAA  773,395 
  Insured       
520  Pennsylvania, General Obligation Bonds, Second Series 2001, 5.000%, 9/15/20 - FSA Insured  9/11 at 101.00  AAA  553,462 
1,720  Total Pennsylvania      1,852,072 
  South Carolina - 7.7%       
1,000  Dorchester County School District 2, South Carolina, Installment Purchase Revenue Bonds, GROWTH,  12/14 at 100.00  A  1,060,600 
  Series 2004, 5.250%, 12/01/20       
10,000  Greenville County School District, South Carolina, Installment Purchase Revenue Bonds, Series 2002,  12/12 at 101.00  AA- (3)  11,437,100 
  5.875%, 12/01/19 (Pre-refunded 12/01/12) (3)       
1,500  Lexington County Health Service District, South Carolina, Hospital Revenue Refunding and Improvement Bonds,  11/13 at 100.00  A  1,661,505 
  Series 2003, 6.000%, 11/01/18       
2,500  South Carolina JOBS Economic Development Authority, Economic Development Revenue Bonds, Bon Secours  11/12 at 100.00  A-  2,644,150 
  Health System Inc., Series 2002A, 5.625%, 11/15/30       
1,720  Tobacco Settlement Revenue Management Authority, South Carolina, Tobacco Settlement Asset-Backed Bonds,  5/11 at 101.00  BBB  1,817,008 
  Series 2001B, 6.000%, 5/15/22       
16,720  Total South Carolina      18,620,363 
  Texas - 8.6%       
5,000  Brazos River Harbor Navigation District, Brazoria County, Texas, Environmental Facilities Revenue Bonds,  5/12 at 101.00  A-  5,422,150 
  Dow Chemical Company Project, Series 2002A-6, 6.250%, 5/15/33 (Mandatory put 5/15/17) (Alternative       
  Minimum Tax)       
6,150  Dallas Independent School District, Dallas County, Texas, General Obligation Refunding Bonds, Series 2002,  2/12 at 100.00  AAA  6,570,537 
  5.250%, 2/15/20       
360  Dallas-Fort Worth International Airport Public Facility Corporation, Texas, Airport Hotel Revenue Bonds,  1/09 at 100.00  AAA  377,629 
  Series 2001, 5.500%, 1/15/20 - FSA Insured       
2,300  Harris County Health Facilities Development Corporation, Texas, Thermal Utility Revenue Bonds, TECO Project,  11/13 at 100.00  AAA  2,369,276 
  Series 2003, 5.000%, 11/15/30 - MBIA Insured       
3,500  Irving Independent School District, Dallas County, Texas, General Obligation Refunding Bonds, Series 2002A,  2/12 at 100.00  AAA  3,602,970 
  5.000%, 2/15/31       
  San Antonio, Texas, Water System Revenue Refunding Bonds, Series 1992:       
95  6.000%, 5/15/16 (Pre-refunded 5/15/07) - MBIA Insured (3)  5/07 at 100.00  AAA  98,487 
465  6.000%, 5/15/16 (Pre-refunded 5/15/12) - MBIA Insured (3)  5/12 at 100.00  AAA  526,915 
1,750  Texas, General Obligation Bonds, Water Financial Assistance Program, Series 2003A, 5.125%, 8/01/42  8/13 at 100.00  Aa1  1,781,605 
  (Alternative Minimum Tax)       
19,620  Total Texas      20,749,569 
  Utah - 0.3%       
775  Utah State Building Ownership Authority, Lease Revenue Bonds, State Facilities Master Lease Program,  11/11 at 100.00  AA+  829,847 
  Series 2001B, 5.250%, 5/15/24       
  Washington - 9.4%       
250  Energy Northwest, Washington, Electric Revenue Refunding Bonds, Columbia Generating Station - Nuclear  7/12 at 100.00  AAA  273,305 
  Project 2, Series 2002C, 5.500%, 7/01/17 - MBIA Insured       
5,700  Snohomish County Public Utility District 1, Washington, Generation System Revenue Bonds, Series 1989,  1/06 at 100.00  Aaa  6,330,477 
  6.750%, 1/01/12       
3,000  Washington State Healthcare Facilities Authority, Revenue Bonds, Catholic Health Initiatives, Series 1997A,  12/07 at 101.00  AAA  3,113,010 
  5.125%, 12/01/17 - MBIA Insured       
9,750  Washington State Healthcare Facilities Authority, Revenue Bonds, Sisters of Providence Health System,  10/11 at 100.00  AAA  10,231,455 
  Series 2001A, 5.125%, 10/01/17 - MBIA Insured       
2,465  Washington State Tobacco Settlement Authority, Tobacco Settlement Asset-Backed Revenue Bonds,  6/13 at 100.00  BBB  2,662,422 
  Series 2002, 6.500%, 6/01/26       
21,165  Total Washington      22,610,669 
  West Virginia - 0.8%       
1,885  Marshall County, West Virginia, Special Obligation Refunding Bonds, Series 1992, 6.500%, 5/15/10  No Opt. Call  AAA  2,033,312 
  Wisconsin - 1.6%       
240  Badger Tobacco Asset Securitization Corporation, Wisconsin, Tobacco Settlement Asset-Backed Bonds,  6/12 at 100.00  BBB  253,514 
  Series 2002, 6.125%, 6/01/27       
1,000  Wisconsin Health and Educational Facilities Authority, Revenue Bonds, Wheaton Franciscan Services Inc.,  8/13 at 100.00  A  1,077,660 
  Series 2003A, 5.500%, 8/15/17       
2,500  Wisconsin, General Obligation Refunding Bonds, Series 2003-3, 5.000%, 11/01/26  11/13 at 100.0  AA-  2,611,000 
3,740  Total Wisconsin      3,942,174 
$ 229,845  Total Long-Term Investments (cost $221,311,381) - 97.3%      234,388,483 
  Short-Term Investments - 0.8%       
2,000  New Jersey Economic Development Authority, Dock Facility Revenue Refunding Bonds, Bayonne/IMTT Project,  No Opt. Call  VMIG-1  2,000,000 
  Variable Rate Demand Obligations, Series 1993C, 3.730%, 12/01/27 (5)       
$ 2,000  Total Short-Term Investments (cost $2,000,000)      2,000,000 
  Total Investments (cost $223,311,381) - 98.1%      236,388,483 
  Other Assets Less Liabilities - 1.9%      4,473,221 
  Net Assets - 100%      $ 240,861,704 

(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. 
(4 )  On December 9, 2002, UAL Corporation, the holding company of United Air Lines, Inc. filed for federal 
  bankruptcy protection. The Adviser determined that it was likely United would not remain current on their 
  interest payment obligations with respect to these bonds and thus has stopped accruing interest. 
(5 )  Security has a maturity of more 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   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 $222,959,331.

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

Gross unrealized:   
    Appreciation  $ 15,504,282  
    Depreciation  (2,075,130 ) 
Net unrealized appreciation (depreciation) of investments  $ 13,429,152  

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 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.