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         811-6693         

        Nuveen Select Tax-Free Income Portfolio 3         
(Exact name of registrant as specified in charter)

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


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

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

Date of fiscal year end:            3/31          

Date of reporting period:         6/30/07         

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

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

Item 1. Schedule of Investments

    Portfolio of Investments (Unaudited)             
    Nuveen Select Tax-Free Income Portfolio 3 (NXR)             
    June 30, 2007             
Principal        Optional Call         
Amount (000)    Description    Provisions (1)    Ratings (2)    Value 
    Long-Term Municipal Bonds – 99.0%             
    Alabama – 0.3%             
$             500    Marshall County Healthcare Authority, Alabama, Revenue Bonds, Series 2002A, 6.250%, 1/01/22    1/12 at 101.00    A–   $   535,615 
    California – 6.9%             
2,105    Azusa Unified School District, Los Angeles County, California, General Obligation Bonds,    7/12 at 100.00    AAA    2,230,711 
     Series 2002, 5.375%, 7/01/21 – FSA Insured             
3,350    California Department of Water Resources, Power Supply Revenue Bonds, Series 2002A,    5/12 at 101.00    A1    3,661,349 
     6.000%, 5/01/14             
2,595    California Health Facilities Financing Authority, Revenue Bonds, Kaiser Permanante System,    4/16 at 100.00    A+    2,607,586 
     Series 2006, 5.000%, 4/01/37             
445    Golden State Tobacco Securitization Corporation, California, Enhanced Tobacco Settlement    6/17 at 100.00    BBB    429,923 
     Asset-Backed Bonds, Series 2007A-1, 4.500%, 6/01/27             
3,000    Golden State Tobacco Securitization Corporation, California, Tobacco Settlement Asset-Backed    6/13 at 100.00    AAA    3,437,040 
     Bonds, Series 2003A-1, 6.750%, 6/01/39 (Pre-refunded 6/01/13)             
250    Santa Ana Unified School District, Orange County, California, General Obligation Bonds, Series    8/10 at 101.00    AAA    264,483 
     2000, 5.700%, 8/01/29 – FGIC Insured             
11,745    Total California            12,631,092 
    Colorado – 6.9%             
1,540    Arkansas River Power Authority, Colorado, Power Revenue Bonds, Series 2006, 5.250%, 10/01/40 –    10/16 at 100.00    AAA    1,616,430 
     XLCA Insured             
400    Colorado Department of Transportation, Certificates of Participation, Series 2004, 5.000%,    6/14 at 100.00    AAA    409,552 
     6/15/34 – MBIA Insured             
2,265    Colorado Health Facilities Authority, Revenue Bonds, Catholic Health Initiatives, Series    3/12 at 100.00    AA (3)    2,402,395 
     2002A, 5.500%, 3/01/22 (ETM)             
1,735    Colorado Health Facilities Authority, Revenue Bonds, Catholic Health Initiatives, Series    3/12 at 100.00    AA (3)    1,843,663 
     2002A, 5.500%, 3/01/22 (Pre-refunded 3/01/12)             
2,700    Denver City and County, Colorado, Airport System Revenue Bonds, Series 1991D, 7.750%, 11/15/13    No Opt. Call    A+    2,957,553 
     (Alternative Minimum Tax)             
3,000    Denver Convention Center Hotel Authority, Colorado, Senior Revenue Bonds, Convention Center    12/13 at 100.00    Aaa    3,163,980 
     Hotel, Series 2003A, 5.000%, 12/01/24 (Pre-refunded 12/01/13) – XLCA Insured             
325    E-470 Public Highway Authority, Colorado, Senior Revenue Bonds, Series 1997A, 5.000%, 9/01/26    9/07 at 101.00    AAA    328,890 
     (Pre-refunded 9/01/07) – MBIA Insured             
11,965    Total Colorado            12,722,463 
    Connecticut – 0.1%             
250    Connecticut Health and Educational Facilities Authority, Revenue Bonds, Bridgeport Hospital    7/07 at 100.00    AAA    251,050 
     Issue, Series 1992A, 6.625%, 7/01/18 – MBIA Insured             
    District of Columbia – 0.1%             
15    District of Columbia, General Obligation Bonds, Series 1993E, 6.000%, 6/01/13 – MBIA Insured (ETM)    9/07 at 100.00    AAA    15,025 
235    District of Columbia, General Obligation Refunding Bonds, Series 1994A-1, 6.500%, 6/01/10 –    No Opt. Call    AAA    251,276 
     MBIA Insured             
250    Total District of Columbia            266,301 
    Florida – 5.5%             
1,000    Hillsborough County Industrial Development Authority, Florida, Hospital Revenue Bonds, Tampa    10/16 at 100.00    A3    1,020,860 
     General Hospital, Series 2006, 5.250%, 10/01/41             
5,020    JEA St. John’s River Power Park System, Florida, Revenue Refunding Bonds, Issue 2, Series    10/11 at 100.00    Aa2    5,169,747 
     2002-17, 5.000%, 10/01/18             
4,000    JEA, Florida, Subordinate Lien Electric System Revenue Bonds, Series 2002D, 4.625%, 10/01/22    10/07 at 100.00    Aa3    3,978,080 
10,020    Total Florida            10,168,687 
    Georgia – 0.4%             
850    Atlanta, Georgia, Airport Facilities Revenue Bonds, Series 1990, 0.000%, 1/01/10 – MBIA    No Opt. Call    AAA    743,385 
     Insured (Alternative Minimum Tax)             
    Illinois – 18.3%             
135    Chicago Metropolitan Housing Development Corporation, Illinois, FHA-Insured Section 8 Assisted    7/07 at 100.00    AA    138,222 
     Housing Development Revenue Refunding Bonds, Series 1992, 6.850%, 7/01/22             
1,930    Illinois Development Finance Authority, Revenue Bonds, Midwestern University, Series 2001B,    5/11 at 101.00    A– (3)    2,067,744 
     5.750%, 5/15/16 (Pre-refunded 5/15/11)             
705    Illinois Finance Authority, Revenue Bonds, University of Chicago, Series 2007, Residual 73TP,    7/17 at 100.00    Aa1    714,398 
     7.203%, 7/01/46 (IF) (4)             
2,185    Illinois Finance Authority, Revenue Bonds, YMCA of Southwest Illinois, Series 2005, 5.000%,    9/15 at 100.00    AA    2,220,747 
     9/01/31 – RAAI Insured             
4,455    Illinois Health Facilities Authority, Remarketed Revenue Bonds, University of Chicago Project,    8/11 at 103.00    Aa1    4,756,069 
     Series 1985A, 5.500%, 8/01/20             
1,500    Illinois Health Facilities Authority, Revenue Bonds, Evangelical Hospitals Corporation, Series    No Opt. Call    N/R (3)    1,775,655 
     1992C, 6.250%, 4/15/22 (ETM)             
2,225    Illinois Health Facilities Authority, Revenue Refunding Bonds, Elmhurst Memorial Healthcare,    1/13 at 100.00    A2    2,415,838 
     Series 2002, 6.250%, 1/01/17             
2,500    Illinois Housing Development Authority, Homeowner Mortgage Revenue Bonds, Series 2006C2,    2/16 at 100.00    AA    2,503,350 
     5.050%, 8/01/27 (Alternative Minimum Tax)             
5,700    Illinois, Sales Tax Revenue Bonds, First Series 2002, 5.000%, 6/15/22    6/13 at 100.00    AAA    5,883,540 
2,000    Illinois, Sales Tax Revenue Bonds, Series 1997X, 5.600%, 6/15/17    12/07 at 101.00    AAA    2,022,700 
1,000    Kankakee & Will Counties Community Unit School District 5, Illinois, General Obligation Bonds,    No Opt. Call    Aaa    477,630 
     Series 2006, 0.000%, 5/01/23 – FSA Insured             
6,000    Metropolitan Pier and Exposition Authority, Illinois, Revenue Refunding Bonds, McCormick Place    6/12 at 101.00    AAA    6,199,556 
     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    1,366,339 
1,000    Yorkville, Illinois, General Obligation Debt Certificates, Series 2003, 5.000%, 12/15/22    12/11 at 100.00    AA (3)    1,042,340 
     (Pre-refunded 12/15/11) – RAAI Insured             
32,635    Total Illinois            33,584,128 
    Indiana – 6.4%             
1,000    Franklin Community Multi-School Building Corporation, Marion County, Indiana, First Mortgage    7/14 at 100.00    AAA    1,035,070 
     Revenue Bonds, Series 2004, 5.000%, 7/15/22 – FGIC Insured             
3,500    Indiana Health Facility Financing Authority, Hospital Revenue Bonds, Methodist Hospitals Inc.,    9/11 at 100.00    A–    3,522,610 
     Series 2001, 5.375%, 9/15/22             
2,500    Indiana Health Facility Financing Authority, Hospital Revenue Refunding Bonds, Columbus    No Opt. Call    AAA    2,814,225 
     Regional Hospital, Series 1993, 7.000%, 8/15/15 – FSA Insured             
2,000    Indianapolis Local Public Improvement Bond Bank, Indiana, Waterworks Project, Series 2002A,    7/12 at 100.00    AAA    2,113,780 
     5.250%, 7/01/33 (Pre-refunded 7/01/12) – MBIA Insured             
2,295    Shelbyville Central Renovation School Building Corporation, Indiana, First Mortgage Bonds,    7/15 at 100.00    AAA    2,195,994 
     Series 2005, 4.375%, 7/15/25 – MBIA Insured             
11,295    Total Indiana            11,681,679 
    Iowa – 5.3%             
2,745    Iowa Finance Authority, Health Facility Revenue Bonds, Care Initiatives Project, Series 2006A,    7/16 at 100.00    BBB–    2,717,852 
     5.000%, 7/01/20             
    Iowa Tobacco Settlement Authority, Tobacco Settlement Asset-Backed Revenue Bonds, Series 2001B:             
3,850     5.300%, 6/01/25 (Pre-refunded 6/01/11)    6/11 at 101.00    AAA    4,026,446 
2,850     5.600%, 6/01/35 (Pre-refunded 6/01/11)    6/11 at 101.00    AAA    3,034,566 
9,445    Total Iowa            9,778,864 
    Kansas – 1.2%             
    Lawrence, Kansas, Hospital Revenue Bonds, Lawrence Memorial Hospital, Series 2006:             
1,425     5.125%, 7/01/26    7/16 at 100.00    A3    1,443,454 
700     4.875%, 7/01/36    7/16 at 100.00    A3    686,147 
2,125    Total Kansas            2,129,601 
    Maine – 0.7%             
1,200    Maine Health and Higher Educational Facilities Authority, Revenue Bonds, Series 1999B, 6.000%,    7/09 at 101.00    AAA    1,256,064 
     7/01/19 – MBIA Insured             
    Massachusetts – 0.8%             
1,000    Massachusetts Development Finance Agency, Resource Recovery Revenue Bonds, Ogden Haverhill    12/08 at 102.00    BBB    1,022,250 
     Associates, Series 1998B, 5.200%, 12/01/13 (Alternative Minimum Tax)             
500    Massachusetts Health and Educational Facilities Authority, Revenue Bonds, Partners HealthCare    7/11 at 101.00    AA    537,860 
     System Inc., Series 2001C, 6.000%, 7/01/17             
1,500    Total Massachusetts            1,560,110 
    Michigan – 3.7%             
1,500    Detroit, Michigan, Sewer Disposal System Revenue Bonds, Second Lien, Series 2006B, 4.625%,    7/16 at 100.00    AAA    1,461,600 
     7/01/34 – FGIC Insured             
400    East Lansing School District, Ingham County, Michigan, General Obligation Bonds, Series 2000,    5/10 at 100.00    AA– (3)    418,076 
     5.625%, 5/01/30 (Pre-refunded 5/01/10)             
2,900    Michigan State Hospital Finance Authority, Hospital Revenue Refunding Bonds, Trinity Health    12/12 at 100.00    Aa2    3,018,668 
     Credit Group, Series 2002C, 5.375%, 12/01/30             
235    Michigan State Hospital Finance Authority, Revenue Refunding Bonds, Detroit Medical Center    8/07 at 100.00    BB–    235,153 
     Obligated Group, Series 1993A, 6.500%, 8/15/18             
1,600    Plymouth-Canton Community School District, Wayne and Washtenaw Counties, Michigan, Unlimited    5/09 at 100.00    AA–    1,617,728 
     Tax General Obligation School Building and Site Bonds, Series 1999, 4.750%, 5/01/18             
6,635    Total Michigan            6,751,225 
    Mississippi – 0.4%             
725    Mississippi Hospital Equipment and Facilities Authority, Revenue Bonds, Baptist Memorial    9/14 at 100.00    N/R    729,292 
     Healthcare, Series 2004B-1, 5.000%, 9/01/24             
    Nebraska – 1.9%             
3,500    Nebraska Public Power District, General Revenue Bonds, Series 2002B, 5.000%, 1/01/33 –    1/13 at 100.00    AAA    3,581,060 
     AMBAC Insured             
    Nevada – 4.9%             
4,095    Director of Nevada State Department of Business and Industry, Revenue Bonds, Las Vegas    1/10 at 100.00    AAA    4,195,573 
     Monorail Project, First Tier, Series 2000, 5.375%, 1/01/40 – AMBAC Insured             
1,680    Reno, Nevada, Capital Improvement Revenue Bonds, Series 2002, 5.500%, 6/01/22 – FGIC Insured    6/12 at 100.00    AAA    1,778,448 
2,830    Reno, Nevada, Capital Improvement Revenue Bonds, Series 2002, 5.500%, 6/01/22 (Pre-refunded    6/12 at 100.00    AAA    3,019,808 
     6/01/12) – FGIC Insured             
8,605    Total Nevada            8,993,829 
    New Hampshire – 0.3%             
530    New Hampshire Housing Finance Authority, Single Family Mortgage Acquisition Bonds, Series    5/11 at 100.00    Aa2    536,159 
     2001A, 5.600%, 7/01/21 (Alternative Minimum Tax)             
    New Jersey – 1.4%             
    Tobacco Settlement Financing Corporation, New Jersey, Tobacco Settlement Asset-Backed Bonds,             
    Series 2003:             
1,000     6.750%, 6/01/39 (Pre-refunded 6/01/13)    6/13 at 100.00    AAA    1,143,980 
1,355     6.250%, 6/01/43 (Pre-refunded 6/01/13)    6/13 at 100.00    AAA    1,514,673 
2,355    Total New Jersey            2,658,653 
    New Mexico – 2.2%             
4,000    University of New Mexico, FHA-Insured Mortgage Hospital Revenue Bonds, Series 2004, 4.625%,    7/14 at 100.00    AAA    3,962,120 
     1/01/25 – FSA Insured             
    New York – 3.6%             
1,180    Dormitory Authority of the State of New York, Second General Resolution Consolidated Revenue    No Opt. Call    A1    1,239,201 
     Bonds, City University System, Series 1990C, 7.500%, 7/01/10             
2,335    Long Island Power Authority, New York, Electric System General Revenue Bonds, Series 2001A,    9/11 at 100.00    A– (3)    2,468,889 
     5.375%, 9/01/21 (Pre-refunded 9/01/11)             
35    New York City, New York, General Obligation Bonds, Series 1991B, 7.000%, 2/01/18    8/07 at 100.00    AA    35,084 
1,000    New York Dormitory Authority, FHA Insured Mortgage Hospital Revenue Bonds, Kaleida    8/16 at 100.00    AAA    984,890 
     Health, Series 2006, 4.700%, 2/15/35 (UB)             
1,850    New York State Tobacco Settlement Financing Corporation, Tobacco Settlement Asset-Backed and    6/10 at 100.00    AA–    1,923,945 
     State Contingency Contract-Backed Bonds, Series 2003B-1C, 5.500%, 6/01/15             
6,400    Total New York            6,652,009 
    North Carolina – 4.2%             
5,000    North Carolina Municipal Power Agency 1, Catawba Electric Revenue Bonds, Series 2003A, 5.250%,    1/13 at 100.00    AAA    5,246,900 
     1/01/18 – MBIA Insured             
2,345    Piedmont Triad Airport Authority, North Carolina, Airport Revenue Bonds, Series 2001A, 5.250%,    7/11 at 101.00    AAA    2,451,346 
     7/01/16 – FSA Insured             
7,345    Total North Carolina            7,698,246 
    Oklahoma – 1.7%             
3,000    Oklahoma Development Finance Authority, Revenue Bonds, St. John Health System, Series 2004,    2/14 at 100.00    AA–    3,041,190 
     5.000%, 2/15/24             
    Pennsylvania – 2.4%             
2,435    Dauphin County Industrial Development Authority, Pennsylvania, Water Development Revenue    No Opt. Call    A–    2,856,620 
     Refunding Bonds, Dauphin Consolidated Water Supply Company, Series 1992B, 6.700%, 6/01/17             
500    Pennsylvania Higher Educational Facilities Authority, Revenue Bonds, Widener University,    7/13 at 100.00    BBB+    515,375 
     Series 2003, 5.250%, 7/15/24             
1,000    Philadelphia Authority for Industrial Development, Pennsylvania, Airport Revenue Bonds, Philadelphia    7/11 at 101.00    AAA    1,050,460 
     Airport System Project, Series 2001A, 5.500%, 7/01/17 – FGIC Insured (Alternative Minimum Tax)             
3,935    Total Pennsylvania            4,422,455 
    South Carolina – 4.9%             
1,500    Lexington County Health Service District, South Carolina, Hospital Revenue Refunding and    11/13 at 100.00    A+    1,614,225 
     Improvement Bonds, Series 2003, 6.000%, 11/01/18             
1,500    Medical University Hospital Authority, South Carolina, FHA-Insured Mortgage Revenue Bonds,    8/14 at 100.00    AAA    1,581,435 
     Series 2004A, 5.250%, 8/15/20 – MBIA Insured             
2,500    South Carolina JOBS Economic Development Authority, Economic Development Revenue Bonds, Bon    11/12 at 100.00    A–    2,596,000 
     Secours Health System Inc., Series 2002A, 5.625%, 11/15/30             
3,010    Tobacco Settlement Revenue Management Authority, South Carolina, Tobacco Settlement    5/11 at 101.00    BBB    3,224,493 
     Asset-Backed Bonds, Series 2001B, 6.375%, 5/15/28             
8,510    Total South Carolina            9,016,153 
    South Dakota – 1.1%             
1,010    South Dakota Health and Educational Facilities Authority, Revenue Bonds, Avera Health, Series    7/12 at 101.00    AAA    1,044,481 
     2002, 5.125%, 7/01/27 – AMBAC Insured             
1,000    South Dakota Health and Educational Facilities Authority, Revenue Bonds, Sioux Valley    11/14 at 100.00    AA–    1,030,300 
     Hospitals, Series 2004A, 5.250%, 11/01/34             
2,010    Total South Dakota            2,074,781 
    Tennessee – 1.1%             
2,000    Knox County Health, Educational and Housing Facilities Board, Tennessee, Hospital Revenue    4/12 at 101.00    Ba2    2,042,880 
     Bonds, Baptist Health System of East Tennessee Inc., Series 2002, 6.375%, 4/15/22             
    Texas – 10.7%             
1,500    Central Texas Regional Mobility Authority, Travis and Williamson Counties, Toll Road Revenue    1/15 at 100.00    AAA    1,520,130 
     Bonds, Series 2005, 5.000%, 1/01/45 – FGIC Insured             
2,500    Harris County Health Facilities Development Corporation, Texas, Thermal Utility Revenue Bonds,    11/13 at 100.00    AAA    2,553,900 
     TECO Project, Series 2003, 5.000%, 11/15/30 – MBIA Insured             
3,000    Houston, Texas, Subordinate Lien Airport System Revenue Bonds, Series 2002B, 5.500%, 7/01/18 –    7/12 at 100.00    AAA    3,172,320 
     FSA Insured             
3,125    Katy Independent School District, Harris, Fort Bend and Waller Counties, Texas, General    2/12 at 100.00    AAA    3,257,688 
     Obligation Bonds, Series 2002A, 5.000%, 2/15/32 (Pre-refunded 2/15/12)             
400    Killeen Independent School District, Bell County, Texas, General Obligation Bonds, Series    2/08 at 100.00    AAA    402,732 
     1998, 5.000%, 2/15/14             
1,425    Killeen Independent School District, Bell County, Texas, General Obligation Bonds, Series    2/08 at 100.00    AAA    1,436,286 
     1998, 5.000%, 2/15/14 (Pre-refunded 2/15/08)             
4,750    Sam Rayburn Municipal Power Agency, Texas, Power Supply System Revenue Refunding Bonds, Series    10/12 at 100.00    AA    5,009,540 
     2002A, 5.500%, 10/01/17 – RAAI Insured             
1,750    Texas, General Obligation Bonds, Water Financial Assistance Program, Series 2003A, 5.125%,    8/13 at 100.00    Aa1    1,767,133 
     8/01/42 (Alternative Minimum Tax)             
500    Victoria, Texas, General Obligation Bonds, Series 2001, 5.000%, 8/15/23 – FGIC Insured    8/11 at 100.00    AAA    513,085 
18,950    Total Texas            19,632,814 
    Washington – 0.2%             
510    Port of Seattle, Washington, Revenue Bonds, Series 2001A, 5.000%, 4/01/31 – FGIC Insured    10/11 at 100.00    AAA    520,353 
    Wisconsin – 1.4%             
2,500    Wisconsin, General Obligation Refunding Bonds, Series 2003-3, 5.000%, 11/01/26    11/13 at 100.00    AA–    2,571,600 
$      175,290    Total Long-Term Municipal Bonds (cost $176,447,499)            182,193,858 
Shares    Description            Value 
    Common Stocks – 0.0%             
    Airlines – 0.0%             
172    UAL Corporation, (5) (6)           $   6,981 
    Total Common Stocks (cost $0)            6,981 
    Total Investments (cost $176,447,499) – 99.0%            182,200,839 
    Floating Rate Obligations – (0.4)%            (665,000) 
    Other Assets Less Liabilities – 1.4%            2,413,512 
    Net Assets – 100%           $   183,949,351 

    The Fund may invest in “zero coupon” securities. A zero coupon security does not pay a regular interest 
    coupon to its holders during the life of the security. Tax-exempt income to the holder of the security comes 
    from accretion of the difference between the original purchase price of the security at issuance and the 
    par value of the security at maturity and is effectively paid at maturity. Such securities are included in the 
    portfolio with a 0.00% coupon rate in their description. The market prices of zero coupon securities 
    generally are more volatile than the market prices of securities that pay interest periodically. 
(1)    Optional Call Provisions: Dates (month and year) and prices of the earliest optional call or redemption. There 
    may be other call provisions at varying prices at later dates. Certain mortgage-backed securities may be 
    subject to periodic principal paydowns. 
(2)    Ratings: Using the higher of Standard & Poor’s or Moody’s rating. Ratings below BBB by Standard & Poor’s 
    Group or Baa by Moody’s Investor Service, Inc. are considered to be below investment grade. 
(3)    Backed by an escrow or trust containing sufficient U.S. Government or U.S. Government agency securities 
    which ensure the timely payment of principal and interest. Such investments are normally considered to be 
    equivalent to AAA rated securities. 
(4)    Investments valued at fair value using methods determined in good faith by, or at the discretion of, the 
    Board of Trustees. 
(5)    Non-income producing. 
(6)    On December 9, 2002, UAL Corporation (“UAL”), the holding company of United Air Lines, Inc. filed for 
    federal bankruptcy protection. The Adviser determined that it was likely that United would not remain 
    current on their interest payment obligations with respect to the bonds previously held and thus the Fund 
    had stopped accruing interest on its UAL bonds. On February 1, 2006, UAL emerged from federal 
    bankruptcy with the acceptance of its reorganization plan by the bankruptcy court. Under the settlement 
    agreement established to meet UAL’s unsecured bond obligations, the bondholders, including the Fund, 
    received three distributions of UAL common stock over the subsequent months, and the bankruptcy court 
    dismissed all unsecured claims of bondholders, including those of the Fund. On May 5, 2006, the Fund 
    liquidated such UAL common stock holdings. On September 29, 2006 and May 30, 2007, the Fund received 
    additional distributions of 532 and 172 shares, respectively, of UAL common stock as a result of its earlier 
    ownership of the UAL bonds. The Fund liquidated 532 shares of such UAL common stock holdings on 
    November 15, 2006. The remaining 172 shares of UAL common stock were still held by the Fund at 
    June 30, 2007. 
N/R    Not rated. 
(ETM)    Escrowed to maturity. 
(IF)    Inverse floating rate investment. 
(UB)    Underlying bond of an inverse floating rate trust reflected as a financing transaction pursuant to the 
    provisions of SFAS No. 140. 

Income Tax Information

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

At June 30, 2007, the cost of investments was $175,734,024.

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

Gross unrealized:     
  Appreciation    $6,191,165 
  Depreciation    (389,429) 
Net unrealized appreciation (depreciation) of investments    $5,801,736 

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 3        

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

Date         August 29, 2007        

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

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

Date         August 29, 2007        

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

Date        August 29, 2007        

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