<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
MSDW S&P 500 INDEX FUND - CLASS D
</LEGEND>
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-2000
<PERIOD-END> AUG-31-2000
<INVESTMENTS-AT-COST> 1,940,165,749
<INVESTMENTS-AT-VALUE> 2,521,304,830
<RECEIVABLES> 10,200,866
<ASSETS-OTHER> 112,978
<OTHER-ITEMS-ASSETS> 68,380
<TOTAL-ASSETS> 2,531,687,054
<PAYABLE-FOR-SECURITIES> (3,607,212)
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> (5,396,427)
<TOTAL-LIABILITIES> (9,003,639)
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1,966,951,682
<SHARES-COMMON-STOCK> 5,670,123
<SHARES-COMMON-PRIOR> 1,173,553
<ACCUMULATED-NII-CURRENT> (4,252,214)
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (22,167,118)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 582,151,065
<NET-ASSETS> 92,303,778
<DIVIDEND-INCOME> 25,846,907
<INTEREST-INCOME> 1,426,040
<OTHER-INCOME> 0
<EXPENSES-NET> (31,525,161)
<NET-INVESTMENT-INCOME> (4,252,214)
<REALIZED-GAINS-CURRENT> (18,897,275)
<APPREC-INCREASE-CURRENT> 322,081,076
<NET-CHANGE-FROM-OPS> 298,931,587
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 0
<DISTRIBUTIONS-OF-GAINS> (61,600)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 5,582,313
<NUMBER-OF-SHARES-REDEEMED> (1,088,746)
<SHARES-REINVESTED> 3,003
<NET-CHANGE-IN-ASSETS> 676,252,366
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 1,712,662
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> (8,627,398)
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> (31,840,573)
<AVERAGE-NET-ASSETS> 44,658,883
<PER-SHARE-NAV-BEGIN> 14.09
<PER-SHARE-NII> 0.11
<PER-SHARE-GAIN-APPREC> 2.11
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> (0.03)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 16.28
<EXPENSE-RATIO> 0.50
</TABLE>
