<TABLE> <S> <C>
<ARTICLE> 6
<SERIES>
<NUMBER> 6
<NAME> MERRILL LYNCH RATED INSTITUTIONAL FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> APR-30-2000
<PERIOD-START> MAY-31-1999
<PERIOD-END> APR-30-2000
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<INVESTMENTS-AT-VALUE> 282,995,939
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<OTHER-ITEMS-LIABILITIES> 131,807
<TOTAL-LIABILITIES> 131,807
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 287,767,291
<SHARES-COMMON-STOCK> 287,767,291
<SHARES-COMMON-PRIOR> 350,842,003
<ACCUMULATED-NII-CURRENT> 0
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<ACCUM-APPREC-OR-DEPREC> (149,392)
<NET-ASSETS> 287,617,899
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 20,518,107
<OTHER-INCOME> 0
<EXPENSES-NET> 1,019,202
<NET-INVESTMENT-INCOME> 19,498,905
<REALIZED-GAINS-CURRENT> 211
<APPREC-INCREASE-CURRENT> (145,189)
<NET-CHANGE-FROM-OPS> 19,353,927
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<DISTRIBUTIONS-OF-GAINS> 4,061
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<NUMBER-OF-SHARES-SOLD> 2,703,108,746
<NUMBER-OF-SHARES-REDEEMED> 2,871,143,082
<SHARES-REINVESTED> 18,133,352
<NET-CHANGE-IN-ASSETS> (149,900,984)
<ACCUMULATED-NII-PRIOR> 0
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<GROSS-ADVISORY-FEES> 742,612
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<PER-SHARE-NAV-END> 1
<EXPENSE-RATIO> 0.28
</TABLE>
