<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
ANNUAL REPORT OF AMERICAN CENTURY MUTUAL FUNDS, INC. AND IS QUALIFIED
IN ITS ENTIRETY BY REFERENCE TO SUCH REPORT.
</LEGEND>
<CIK> 0000100334
<NAME> AMERICAN CENTURY MUTUAL FUNDS, INC.
<SERIES>
<NUMBER> 31
<NAME> ULTRA FUND - INVESTOR CLASS
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> OCT-31-2000
<PERIOD-END> OCT-31-2000
<INVESTMENTS-AT-COST> 25,691,332
<INVESTMENTS-AT-VALUE> 39,771,182
<RECEIVABLES> 339,462
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 40,110,644
<PAYABLE-FOR-SECURITIES> 310,939
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 53,862
<TOTAL-LIABILITIES> 364,801
<SENIOR-EQUITY> 9,278
<PAID-IN-CAPITAL-COMMON> 21,551,044
<SHARES-COMMON-STOCK> 927,813
<SHARES-COMMON-PRIOR> 946,601
<ACCUMULATED-NII-CURRENT> (272,880)
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 4,378,963
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 14,079,438
<NET-ASSETS> 39,745,843
<DIVIDEND-INCOME> 121,651
<INTEREST-INCOME> 25,871
<OTHER-INCOME> 0
<EXPENSES-NET> 420,402
<NET-INVESTMENT-INCOME> (272,880)
<REALIZED-GAINS-CURRENT> 4,459,067
<APPREC-INCREASE-CURRENT> (668,629)
<NET-CHANGE-FROM-OPS> 3,517,558
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 0
<DISTRIBUTIONS-OF-GAINS> (1,259,980)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 446,378
<NUMBER-OF-SHARES-REDEEMED> (465,217)
<SHARES-REINVESTED> 29,187
<NET-CHANGE-IN-ASSETS> 3,559,931
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 1,196,168
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 418,063
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 420,402
<AVERAGE-NET-ASSETS> 41,364,445
<PER-SHARE-NAV-BEGIN> 38.97
<PER-SHARE-NII> (0.28)
<PER-SHARE-GAIN-APPREC> 4.14
<PER-SHARE-DIVIDEND> 0.00
<PER-SHARE-DISTRIBUTIONS> (1.38)
<RETURNS-OF-CAPITAL> 0.00
<PER-SHARE-NAV-END> 41.45
<EXPENSE-RATIO> 0.99
</TABLE>
