WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000897513
<NAME> ACM MUNICIPAL SECURITIES INCOME FUND
<SERIES>
<NUMBER> 001
<NAME> ACM MUNICIPAL SECURITIES INCOME FUND
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> OCT-31-2000
<PERIOD-END> APR-30-2000
<INVESTMENTS-AT-COST> 205,840,719
<INVESTMENTS-AT-VALUE> 208,774,677
<RECEIVABLES> 3,744,560
<ASSETS-OTHER> 55,140
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<PAYABLE-FOR-SECURITIES> 1,494,780
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 376,134
<TOTAL-LIABILITIES> 0
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 238,387,542
<SHARES-COMMON-STOCK> 10,815,006
<SHARES-COMMON-PRIOR> 10,815,006
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> (814,544)
<ACCUMULATED-NET-GAINS> (29,803,494)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 2,933,958
<NET-ASSETS> (21,630,012)
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 6,954,029
<OTHER-INCOME> 0
<EXPENSES-NET> 975,597
<NET-INVESTMENT-INCOME> 5,978,432
<REALIZED-GAINS-CURRENT> (8,555,063)
<APPREC-INCREASE-CURRENT> 3,927,050
<NET-CHANGE-FROM-OPS> 1,350,419
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (5,978,432)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> (518,160)
<NUMBER-OF-SHARES-SOLD> 0
<NUMBER-OF-SHARES-REDEEMED> 0
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> (5,146,173)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (21,248,430)
<OVERDISTRIB-NII-PRIOR> (80,631)
<OVERDIST-NET-GAINS-PRIOR> 0
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<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 975,597
<AVERAGE-NET-ASSETS> 210,703,000
<PER-SHARE-NAV-BEGIN> 11.64
<PER-SHARE-NII> 0.55
<PER-SHARE-GAIN-APPREC> (0.43)
<PER-SHARE-DIVIDEND> (0.39)
<PER-SHARE-DISTRIBUTIONS> (0.16)
<RETURNS-OF-CAPITAL> (0.05)
<PER-SHARE-NAV-END> 11.16
<EXPENSE-RATIO> 0.93
[AVG-DEBT-OUTSTANDING] 0
[AVG-DEBT-PER-SHARE] 0.00
</TABLE>
