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 May 31, 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:  July 28, 2006


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



                                   By:  /s/ Maryanne L. Roepke
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                                        Maryanne L. Roepke
                                        Sr. Vice President, Treasurer, and
                                        Chief Financial Officer
                                        (chief financial officer)