<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
this schedule contains summary financial information from mason street funds,
inc. index 400 stock fund, 09/30/00 financial statements class b.
</LEGEND>
<CIK> 0001023744
<NAME> MASON STREET FUNDS, INC.
<SERIES>
<NUMBER> 102
<NAME> INDEX 400 STOCK FUND CLASS B
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> MAR-31-2001
<PERIOD-START> APR-01-2000
<PERIOD-END> SEP-30-2000
<INVESTMENTS-AT-COST> 37,159,217
<INVESTMENTS-AT-VALUE> 40,853,476
<RECEIVABLES> 187,803
<ASSETS-OTHER> 68,741
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 41,110,020
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 134,574
<TOTAL-LIABILITIES> 134,574
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 32,346,503
<SHARES-COMMON-STOCK> 385,264
<SHARES-COMMON-PRIOR> 304,177
<ACCUMULATED-NII-CURRENT> 127,824
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 4,813,885
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 3,687,234
<NET-ASSETS> 40,975,446
<DIVIDEND-INCOME> 192,031
<INTEREST-INCOME> 93,483
<OTHER-INCOME> 0
<EXPENSES-NET> (187,394)
<NET-INVESTMENT-INCOME> 98,120
<REALIZED-GAINS-CURRENT> 2,527,120
<APPREC-INCREASE-CURRENT> 379,913
<NET-CHANGE-FROM-OPS> 3,005,153
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 0
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 82,316
<NUMBER-OF-SHARES-REDEEMED> 1,229
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 5,371,093
<ACCUMULATED-NII-PRIOR> 29,538
<ACCUMULATED-GAINS-PRIOR> 2,290,705
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 74,149
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 282,056
<AVERAGE-NET-ASSETS> 4,103,480
<PER-SHARE-NAV-BEGIN> 11.84
<PER-SHARE-NII> (0.01)
<PER-SHARE-GAIN-APPREC> 0.92
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 12.75
<EXPENSE-RATIO> 1.60
</TABLE>
