<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM
THE ANNUAL REPORT OF AMERICAN CENTURY MUNICIPAL TRUST AND
IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH REPORT.
</LEGEND>
<CIK> 0000746458
<NAME> AMERICAN CENTURY MUNICIPAL TRUST
<SERIES>
<NUMBER> 10
<NAME> HIGH YIELD MUNICIPAL
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> MAY-31-2000
<PERIOD-END> MAY-31-2000
<INVESTMENTS-AT-COST> 28,842
<INVESTMENTS-AT-VALUE> 27,584
<RECEIVABLES> 523
<ASSETS-OTHER> 1,113
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 29,220
<PAYABLE-FOR-SECURITIES> 994
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 37
<TOTAL-LIABILITIES> 1,031
<SENIOR-EQUITY> 30
<PAID-IN-CAPITAL-COMMON> 31,030
<SHARES-COMMON-STOCK> 3,025
<SHARES-COMMON-PRIOR> 3,598
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (1,613)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> (1,258)
<NET-ASSETS> 28,189
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 1,964
<OTHER-INCOME> 0
<EXPENSES-NET> 216
<NET-INVESTMENT-INCOME> 1,788
<REALIZED-GAINS-CURRENT> (1,610)
<APPREC-INCREASE-CURRENT> (1,337)
<NET-CHANGE-FROM-OPS> (1,159)
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (1,788)
<DISTRIBUTIONS-OF-GAINS> (19)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 1,320
<NUMBER-OF-SHARES-REDEEMED> (2,595)
<SHARES-REINVESTED> 142
<NET-CHANGE-IN-ASSETS> (13,879)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 214
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 216
<AVERAGE-NET-ASSETS> 33,636
<PER-SHARE-NAV-BEGIN> 10.12
<PER-SHARE-NII> 0.51
<PER-SHARE-GAIN-APPREC> (0.79)
<PER-SHARE-DIVIDEND> (0.51)
<PER-SHARE-DISTRIBUTIONS> (0.01)
<RETURNS-OF-CAPITAL> 0.00
<PER-SHARE-NAV-END> 9.32
<EXPENSE-RATIO> 0.52
</TABLE>
