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 World Mutual
Funds, Inc. (the  "Registrant") on Form N-CSR for the period ending November 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:   January 29, 2007



                                            /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)