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:            03/31          

Date of reporting period:          06/30/05         

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)             
                   June 30, 2005             
 
 
 
Principal        Optional Call        Market 
Amount (000)    Description    Provisions*    Ratings**    Value 
 
    Alaska - 1.1%             
$ 2,475    Alaska Municipal Bond Bank Authority, General Obligation Bonds, Series 2003E, 5.250%, 12/01/23 -    12/13 at 100.00    AAA    $ 2,752,175 
    MBIA Insured             
 
    California - 4.3%             
2,000    Alameda Corridor Transportation Authority, California, Subordinate Lien Revenue Bonds, Series    10/17 at 100.00    AAA    1,500,680 
    2004A, 0.000%, 10/01/25 - AMBAC Insured             
3,325    California Department of Water Resources, Power Supply Revenue Bonds, Series 2002A, 6.000%,    5/12 at 101.00    A2    3,871,963 
    5/01/14             
200    Contra Costa County, California, Certificates of Participation Refunding, Merrithew Memorial    11/07 at 102.00    AAA    214,418 
    Hospital Replacement Project, 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    3,379,380 
    Series 2003A-1, 6.750%, 6/01/39             
1,130    Los Angeles Department of Water and Power, California, Waterworks Revenue Refunding Bonds, Series    7/11 at 100.00    AAA    1,183,370 
    2001A, 5.125%, 7/01/41 - FGIC Insured             
365    Los Angeles, California, Parking System Revenue Bonds, Series 1999-A, 5.250%, 5/01/29 - AMBAC    5/09 at 101.00    AAA    391,262 
    Insured             
 
    Colorado - 13.5%             
    Colorado Health Facilities Authority, Revenue Bonds, Catholic Health Initiatives, Series 2002A:             
1,700    5.500%, 3/01/22    3/12 at 100.00    AA***    1,908,284 
1,300    5.500%, 3/01/22    3/12 at 100.00    AA    1,432,262 
1,000    Colorado Water Resources and Power Development Authority, Small Water Resources Revenue Bonds,    11/10 at 100.00    AAA    1,119,280 
    Series 2000A, 5.800%, 11/01/20 - FGIC Insured             
5,000    Denver City and County, Colorado, Airport System Revenue Refunding Bonds, Series 2001A, 5.625%,    11/11 at 100.00    AAA    5,510,600 
    11/15/17 (Alternative Minimum Tax) - FGIC Insured             
10,750    Denver City and County, Colorado, Airport System Revenue Bonds, Series 1991D, 7.750%, 11/15/13    No Opt. Call    A    12,732,408 
    (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    665,837 
    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    239,285 
    MBIA Insured             
    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    1,062,400 
3,000    5.000%, 12/01/23 - XLCA Insured    12/13 at 100.00    AAA    3,180,630 
5,000    E-470 Public Highway Authority, Colorado, Senior Revenue Bonds, Series 2000B, 0.000%, 9/01/28    9/10 at 31.42    AAA    1,322,850 
    (Pre-refunded to 9/01/10) - MBIA Insured             
3,160    Northwest Parkway Public Highway Authority, Colorado, Revenue Bonds, Senior Series 2001A, 5.500%,    6/11 at 102.00    AAA    3,532,248 
    6/15/20 - AMBAC Insured             
 
    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    1,052,820 
    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    290,080 
    AMBAC Insured             
 
    Florida - 7.1%             
450    Escambia County, Florida, Pollution Control Revenue Bonds, Champion International Corporation,    12/05 at 100.00    BBB    452,754 
    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    10,838,200 
    5.000%, 10/01/17             
6,100    JEA St. John's River Power Park System, Florida, Revenue Refunding Bonds, Issue Two, Series Nine,    10/05 at 100.00    Aa2    6,152,887 
    5.250%, 10/01/21             
 
    Hawaii - 0.6%             
1,330    Hawaii, Certificates of Participation, Kapolei State Office Building, Series 1998A, 5.000%,    11/08 at 101.00    AAA    1,415,559 
    5/01/17 - 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    4,126,555 
2,600    5.650%, 12/01/17 - FGIC Insured    12/08 at 100.00    AAA    2,805,140 
2,500    Chicago, Illinois, Special Facility Revenue Refunding Bonds, O'Hare International Airport, United    No Opt. Call    N/R    413,375 
    Air Lines Inc. Project, Series 2001C, 6.300%, 5/01/16 #             
1,000    DuPage County Community School District 200, Wheaton, Illinois, General Obligation Bonds, Series    11/13 at 100.00    Aaa    1,104,970 
    2003B, 5.250%, 11/01/20 - FSA Insured             
1,000    Illinois Educational Facilities Authority, Revenue Bonds, Midwestern University, Series 1998B,    5/08 at 101.00    A    1,042,720 
    5.500%, 5/15/18 - ACA Insured             
4,000    Illinois Finance Authority, Revenue Bonds, Northwestern Memorial Hospital, Series 2004A, 5.500%,    8/14 at 100.00    AA+    4,363,040 
    8/15/43             
1,530    Illinois Health Facilities Authority, Revenue Refunding Bonds, Evangelical Hospitals Corporation,    No Opt. Call    N/R***    1,626,237 
    Series 1992B, 6.500%, 4/15/09             
300    Illinois Health Facilities Authority, Revenue Bonds, Rush-Presbyterian St. Luke's Medical Center    11/05 at 100.00    AAA    302,211 
    Obligated Group, Series 1993, 5.250%, 11/15/20 - MBIA Insured             
1,320    Illinois Health Facilities Authority, Revenue Bonds, Decatur Memorial Hospital, Series 2001,    10/11 at 100.00    A    1,418,960 
    5.600%, 10/01/16             
2,700    Illinois Health Facilities Authority, Revenue Bonds, Lake Forest Hospital, Series 2002A, 6.000%,    7/12 at 100.00    A-    3,011,283 
    7/01/17             
2,275    Illinois Health Facilities Authority, Revenue Refunding Bonds, Elmhurst Memorial Healthcare, Series    1/13 at 100.00    A2    2,577,962 
    2002, 6.250%, 1/01/17             
600    Illinois Educational Facilities Authority, Student Housing Revenue Bonds, Educational Advancement    5/12 at 101.00    Baa2    650,028 
    Foundation Fund, University Center Project, Series 2002, 6.000%, 5/01/22             
3,125    Metropolitan Pier and Exposition Authority, Illinois, Revenue Bonds, McCormick Place Expansion    No Opt. Call    AAA    1,925,656 
    Project, Series 1992A, 0.000%, 6/15/17 - FGIC Insured             
5,000    Metropolitan Pier and Exposition Authority, Illinois, Revenue Refunding Bonds, McCormick Place    6/12 at 101.00    AAA    5,389,500 
    Expansion 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    1,420,575 
    Yorkville, Illinois, General Obligation Debt Certificates, Series 2003:             
1,000    5.000%, 12/15/19 - RAAI Insured    12/11 at 100.00    AA    1,044,820 
1,000    5.000%, 12/15/20 - RAAI Insured    12/11 at 100.00    AA    1,042,530 
 
    Indiana - 8.3%             
5,000    Duneland School Building Corporation, Indiana, First Mortgage Refunding Bonds, Series 1999,    2/09 at 101.00    AAA    5,365,500 
    5.125%, 2/01/18 - MBIA Insured             
1,000    Franklin Community Multi-School Building Corporation, Marion County, Indiana, First Mortgage    7/14 at 100.00    AAA    1,070,140 
    Revenue Bonds, Series 2004, 5.000%, 7/15/22 - FGIC Insured             
2,000    Indiana Health Facility Financing Authority, Hospital Revenue Refunding Bonds, Columbus Regional    No Opt. Call    AAA    2,442,500 
    Hospital, 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    10,663,898 
    5.125%, 7/01/21 - MBIA Insured             
750    West Clark 2000 School Building Corporation, Clark County, Indiana, First Mortgage Bonds, Series    1/15 at 100.00    AAA    804,990 
    2005, 5.000%, 7/15/22 - MBIA Insured             
 
    Kansas - 0.3%             
750    Wamego, Kansas, Pollution Control Revenue Bonds, Kansas Gas and Electric Company, Series 2004,    6/14 at 100.00    AAA    821,865 
    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,    10/08 at 101.00    AAA    1,156,111 
    5.125%, 10/01/18 - MBIA Insured             
 
    Louisiana - 0.4%             
1,000    Tobacco Settlement Financing Corporation, Louisiana, Tobacco Settlement Asset-Backed Bonds, Series    5/11 at 101.00    BBB    1,041,460 
    2001B, 5.875%, 5/15/39             
 
    Massachusetts - 0.2%             
500    Massachusetts Health and Educational Facilities Authority, Revenue Bonds, Partners HealthCare    7/11 at 101.00    AA-    566,130 
    System Inc., Series 2001C, 6.000%, 7/01/17             
 
    Michigan - 1.6%             
2,900    Michigan State Hospital Finance Authority, Hospital Revenue Refunding Bonds, Trinity Health Credit    12/12 at 100.00    AA-    3,093,285 
    Group, Series 2002C, 5.375%, 12/01/30             
1,000    Michigan State Hospital Finance Authority, Hospital Revenue Bonds, Detroit Medical Center Obligated    8/08 at 101.00    BB-    916,110 
    Group, Series 1998A, 5.125%, 8/15/18             
 
    Minnesota - 0.2%             
395    Minnesota Housing Finance Agency, Single Family Mortgage Revenue Bonds, Series 1995A, 5.200%,    7/08 at 101.00    AA+    410,314 
    1/01/17             
 
    Mississippi - 1.6%             
3,600    Calhoun County, Mississippi, Solid Waste Disposal Revenue Bonds, Weyerhauser Company Project,    4/07 at 103.00    BBB    3,847,824 
    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    2,698,550 
    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    1,180,260 
3,500    0.000%, 1/01/22 - AMBAC Insured    No Opt. Call    AAA    1,660,435 
6,025    5.375%, 1/01/40 - AMBAC Insured    1/10 at 100.00    AAA    6,422,048 
4,070    Reno, Nevada, Capital Improvement Revenue Bonds, Series 2002, 5.500%, 6/01/21 - FGIC Insured    6/12 at 100.00    AAA    4,513,508 
 
    New Hampshire - 0.3%             
635    New Hampshire Housing Finance Agency, Single Family Mortgage Acquisition Bonds, Series 2001A,    5/11 at 100.00    Aa2    641,407 
    5.600%, 7/01/21 (Alternative Minimum Tax)             
 
    New Jersey - 1.8%             
2,500    New Jersey Health Care Facilities Financing Authority, Revenue Bonds, Somerset Medical Center,    7/13 at 100.00    Baa3    2,610,925 
    Series 2003, 5.500%, 7/01/23             
1,835    Tobacco Settlement Financing Corporation, New Jersey, Tobacco Settlement Asset-Backed Bonds, Series    6/12 at 100.00    BBB    1,909,152 
    2002, 5.750%, 6/01/32             
 
    New Mexico - 1.7%             
4,000    University of New Mexico, FHA-Insured Mortgage Hospital Revenue Bonds, Series 2004, 4.625%,    7/14 at 100.00    AAA    4,069,280 
    7/01/25 - FSA Insured             
 
    New York - 1.3%             
450    Long Island Power Authority, New York, Electric System General Revenue Bonds, Series 1998A,    6/08 at 101.00    AAA    475,596 
    5.125%, 12/01/22 - FSA Insured             
1,000    Dormitory Authority of the State of New York, FHA-Insured Mortgage Revenue Bonds, Kaleida Health,    2/14 at 100.00    AAA    1,063,830 
    Series 2004, 5.050%, 2/15/25             
1,600    Dormitory Authority of the State of New York, Revenue Bonds, Mount Sinai NYU Health Obligated    7/10 at 101.00    Ba1    1,705,872 
    Group, Series 2000A, 6.500%, 7/01/17             
 
    North Carolina - 1.4%             
500    Appalachian State University, North Carolina, Utilities System Revenue Refunding Bonds, Series    5/08 at 102.00    AAA    530,225 
    1998, 5.000%, 5/15/24 - MBIA Insured             
2,195    North Carolina Eastern Municipal Power Agency, Power System Revenue Refunding Bonds, Series 1993B,    7/05 at 100.00    BBB    2,235,498 
    5.500%, 1/01/21             
500    Raleigh Durham Airport Authority, North Carolina, Airport Revenue Bonds, Series 2001A, 5.250%,    5/11 at 101.00    Aaa    548,360 
    11/01/17 - FGIC Insured             
 
    Ohio - 0.6%             
300    Lebanon, Ohio, Electric System Mortgage Revenue Bonds, Series 2001, 5.500%, 12/01/17 - AMBAC    12/10 at 101.00    AAA    335,091 
    Insured             
1,125    Ohio Housing Finance Agency, GNMA Mortgage-Backed Securities Program Residential Mortgage    9/07 at 102.00    Aaa    1,176,300 
    Remarketed Revenue Bonds, Series 1997A-1, 6.050%, 9/01/17 (Alternative Minimum Tax)             
 
    Oklahoma - 1.7%             
4,000    Oklahoma Development Finance Authority, Revenue Bonds, St. John Health System, Series 2004,    2/14 at 100.00    AA    4,171,960 
    5.000%, 2/15/24             
 
    Pennsylvania - 0.8%             
520    Pennsylvania, General Obligation Bonds, Second Series 2001, 5.000%, 9/15/20 - FSA Insured    9/11 at 101.00    AAA    564,621 
500    Pennsylvania Higher Educational Facilities Authority, Revenue Bonds, Widener University, Series    7/13 at 100.00    BBB+    527,300 
    2003, 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    790,804 
    Insured             
 
    South Carolina - 7.3%             
10,000    Greenville County School District, South Carolina, Installment Purchase Revenue Bonds, Series 2002,    12/12 at 101.00    AA-***    11,740,300 
    5.875%, 12/01/19 (Pre-refunded to 12/01/12)             
1,500    Lexington County Health Service District, South Carolina, Hospital Revenue Refunding and    11/13 at 100.00    A    1,693,440 
    Improvement Bonds, 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-    2,670,825 
    Health System Inc., Series 2002A, 5.625%, 11/15/30             
1,720    Tobacco Settlement Revenue Management Authority, South Carolina, Tobacco Settlement Asset-Backed    5/11 at 101.00    BBB    1,822,512 
    Bonds, Series 2001B, 6.000%, 5/15/22             
 
    Texas - 8.6%             
5,000    Brazos River Harbor Navigation District, Brazoria County, Texas, Environmental Facilities Revenue    5/12 at 101.00    A-    5,463,700 
    Bonds, Dow Chemical Company Project, Series 2002A-6, 6.250%, 5/15/33 (Alternative Minimum Tax)             
    (Mandatory put 5/15/17)             
360    Dallas-Fort Worth International Airport Public Facility Corporation, Texas, Airport Hotel Revenue    1/09 at 100.00    AAA    382,918 
    Bonds, Series 2001, 5.500%, 1/15/20 - FSA Insured             
6,150    Dallas Independent School District, Dallas County, Texas, General Obligation Refunding Bonds,    2/12 at 100.00    AAA    6,682,713 
    Series 2002, 5.250%, 2/15/20             
2,300    Harris County Health Facilities Development Corporation, Texas, Thermal Utility Revenue Bonds, TECO    11/13 at 100.00    AAA    2,422,038 
    Project, Series 2003, 5.000%, 11/15/30 - MBIA Insured             
3,500    Irving Independent School District, Dallas County, Texas, General Obligation Refunding Bonds,    2/12 at 100.00    AAA    3,659,285 
    Series 2002A, 5.000%, 2/15/31             
    San Antonio, Texas, Water System Revenue Refunding Bonds, Series 1992:             
465    6.000%, 5/15/16 (Pre-refunded to 5/15/12) - MBIA Insured    5/12 at 100.00    AAA    564,440 
95    6.000%, 5/15/16 (Pre-refunded to 5/15/07) - MBIA Insured    5/07 at 100.00    AAA    100,655 
1,750    Texas, General Obligation Bonds, Water Financial Assistance Program, Series 2003A, 5.125%, 8/01/42    8/13 at 100.00    Aa1    1,823,868 
    (Alternative Minimum Tax)             
 
    Utah - 0.3%             
775    Utah State Building Authority, Lease Revenue Bonds, State Facilities Master Lease Program, Series    11/11 at 100.00    AA+    843,092 
    2001B, 5.250%, 5/15/24             
 
    Washington - 9.4%             
250    Energy Northwest, Washington, Electric Revenue Refunding Bonds, Columbia Generating Station,    7/12 at 100.00    AAA    279,252 
    Nuclear 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    7/05 at 100.00    Aaa    6,506,379 
    1989, 6.750%, 1/01/12             
2,480    Washington State Tobacco Settlement Authority, Tobacco Settlement Asset-Backed Revenue Bonds,    6/13 at 100.00    BBB    2,720,684 
    2002, 6.500%, 6/01/26             
3,000    Washington State Healthcare Facilities Authority, Revenue Bonds, Catholic Health Initiatives,    12/07 at 101.00    AAA    3,164,580 
    Series 1997A, 5.125%, 12/01/17 - MBIA Insured             
9,750    Washington State Healthcare Facilities Authority, Revenue Bonds, Sisters of Providence Health    10/11 at 100.00    AAA    10,434,450 
    System, Series 2001A, 5.125%, 10/01/17 - MBIA Insured             
 
    West Virginia - 0.9%             
1,885    Marshall County, West Virginia, Special Obligation Refunding Bonds, Series 1992, 6.500%, 5/15/10    No Opt. Call    AAA    2,086,469 
 
    Wisconsin - 1.6%             
240    Badger Tobacco Asset Securitization Corporation, Wisconsin, Tobacco Settlement Asset-Backed Bonds,    6/12 at 100.00    BBB    254,895 
    Series 2002, 6.125%, 6/01/27             
2,500    Wisconsin, General Obligation Refunding Bonds, Series 2003-3, 5.000%, 11/01/26    11/13 at 100.00    AA-    2,658,300 
1,000    Wisconsin Health and Educational Facilities Authority, Revenue Bonds, Wheaton Franciscan Services    8/13 at 100.00    A    1,092,900 
    Inc., Series 2003A, 5.500%, 8/15/17             

$ 233,075    Total Long-Term Investments (cost $224,455,588) - 98.7%       

241,566,038 

    Short-Term Investments - 0.4%         
1,000    New York City, New York, General Obligation Bonds, Variable Rate Demand Obligations, Fiscal Series    A-1+    1,000,000 
    2002A-7, 2.230%, 11/01/24 - AMBAC Insured +         
$ 1,000    Total Short-Term Investments (cost $1,000,000)        1,000,000 
    Total Investments (cost $225,455,588) - 99.1%        242,566,038 
    Other Assets Less Liabilities - 0.9%        2,221,154 
    Net Assets - 100%        $244,787,192 

*    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.     
**    Ratings: Using the higher of Standard & Poor's or Moody's rating.     
***    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.     
#    On December 9 2002, UAL Corporation, the holdong 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.     
N/R    Investment is not rated.     
+    Security has a maturity of more than one year, but has variable rate and demand features which qualify it as a     
    short-term security. 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.     
 
    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 income on taxable market     
    discount securities and timing differences in recognizing certain gains and losses on investment transactions.     
 
    At June 30, 2005, the cost of investments was $225,130,255.     
 
    Gross unrealized appreciation and gross unrealized depreciation of investments at June 30, 2005, were as     
    follows:     
 
    Gross unrealized:     
       Appreciation    $19,516,575 
       Depreciation    (2,080,792) 
 
    Net unrealized appreciation of investments    $17,435,783 

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--Vice President and Secretary        

Date         08/26/05        

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--Chief Administrative Officer (principal executive officer)        

Date         08/26/05        

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

Date         08/26/05        

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