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 Municipal
Trust (the "Registrant") on Form N-CSR for the period ending May 31, 2004 (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: August 6, 2004


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


                                     /s/ Maryanne L. Roepke
                                     -------------------------------------
                                     Maryanne L. Roepke
                                     Sr. Vice President, Treasurer, and
                                     Chief Accounting Officer
                                     (chief financial officer)