WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000319676
<NAME> CALVERT TAX-FREE RESERVES
<SERIES>
<NUMBER> 611
<NAME> MONEY MARKET PORTFOLIO, CLASS O
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> JUN-30-2000
<INVESTMENTS-AT-COST> 1529115
<INVESTMENTS-AT-VALUE> 1529115
<RECEIVABLES> 14669
<ASSETS-OTHER> 9311
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 1553095
<PAYABLE-FOR-SECURITIES> 18292
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 2460
<TOTAL-LIABILITIES> 20752
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1230868
<SHARES-COMMON-STOCK> 1230981
<SHARES-COMMON-PRIOR> 1278187
<ACCUMULATED-NII-CURRENT> (5)
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (183)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 1230680
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 27407
<OTHER-INCOME> 0
<EXPENSES-NET> 4085
<NET-INVESTMENT-INCOME> 23322
<REALIZED-GAINS-CURRENT> (17)
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 23305
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (23355)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 763600
<NUMBER-OF-SHARES-REDEEMED> (833832)
<SHARES-REINVESTED> 23026
<NET-CHANGE-IN-ASSETS> (47256)
<ACCUMULATED-NII-PRIOR> 73
<ACCUMULATED-GAINS-PRIOR> (213)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 1252
<INTEREST-EXPENSE> 4214
<GROSS-EXPENSE> 0
<AVERAGE-NET-ASSETS> 1261060
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.019
<PER-SHARE-GAIN-APPREC> 0.0
<PER-SHARE-DIVIDEND> (0.019)
<PER-SHARE-DISTRIBUTIONS> 0.0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.65
[AVG-DEBT-OUTSTANDING] 0
[AVG-DEBT-PER-SHARE] 0
</TABLE>
