<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000820611
<NAME> MERRILL LYNCH INSTITUTIONAL INDEX SERIES
<SERIES>
<NUMBER> 010
<NAME> MERRILL LYNCH EQUITY INDEX FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> APR-30-2000
<PERIOD-START> MAY-01-1999
<PERIOD-END> APR-30-2000
<INVESTMENTS-AT-COST> 0
<INVESTMENTS-AT-VALUE> 0
<RECEIVABLES> 0
<ASSETS-OTHER> 247000
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 247000
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 147000
<TOTAL-LIABILITIES> 147000
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 100000
<SHARES-COMMON-STOCK> 10000
<SHARES-COMMON-PRIOR> 10000
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 100000
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 0
<OTHER-INCOME> 0
<EXPENSES-NET> 0
<NET-INVESTMENT-INCOME> 0
<REALIZED-GAINS-CURRENT> 0
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 0
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 0
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 0
<NUMBER-OF-SHARES-REDEEMED> 0
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 0
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 0
<AVERAGE-NET-ASSETS> 100000
<PER-SHARE-NAV-BEGIN> 10.00
<PER-SHARE-NII> 0
<PER-SHARE-GAIN-APPREC> 0
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.00
<EXPENSE-RATIO> 0
</TABLE>
