EXHIBIT 99.906CERT



     CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
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     In  connection  with the  shareholder  report of American  Century  Capital
Portfolios,  Inc.  (the  "Registrant")  on  Form  N-CSR  for the  period  ending
September 30, 2006 (the "Report"),  we, the  undersigned,  certify,  pursuant to
Section 906 of the Sarbanes-Oxley Act of 2002, that:

          (1)  The Report fully complies with the requirements of Section 15(d)
               of the Securities Exchange Act of 1934; and

          (2)  The information contained in the Report fairly presents, in all
               material respects, the financial condition and results of
               operations of the Registrant.


Dated:  November 28, 2006



                                     /s/  William M. Lyons
                                     ------------------------------------
                                     William M. Lyons
                                     President
                                     (chief executive officer)



                                     /s/  Robert J. Leach
                                     ------------------------------------
                                     Robert J. Leach
                                     Vice President, Treasurer, and
                                     Chief Financial Officer
                                     (chief financial officer)