<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000225604
<NAME> MFS SERIES TRUST III
<SERIES>
<NUMBER> 021
<NAME> MFS MUNICIPAL HIGH INCOME FUND CLASS A
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> JAN-31-2001
<PERIOD-START> FEB-01-2000
<PERIOD-END> JUL-31-2000
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<TOTAL-LIABILITIES> 7646106
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<PAID-IN-CAPITAL-COMMON> 1523991434
<SHARES-COMMON-STOCK> 119334074
<SHARES-COMMON-PRIOR> 122221615
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> (1418469)
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<OVERDISTRIBUTION-GAINS> (163322696)
<ACCUM-APPREC-OR-DEPREC> (21077318)
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<EXPENSES-NET> (6544044)
<NET-INVESTMENT-INCOME> 40776157
<REALIZED-GAINS-CURRENT> (9529711)
<APPREC-INCREASE-CURRENT> 30601403
<NET-CHANGE-FROM-OPS> 61847849
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (31836214)
<DISTRIBUTIONS-OF-GAINS> 0
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<NUMBER-OF-SHARES-SOLD> 5966268
<NUMBER-OF-SHARES-REDEEMED> (10263614)
<SHARES-REINVESTED> 1409805
<NET-CHANGE-IN-ASSETS> (4984104)
<ACCUMULATED-NII-PRIOR> 0
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<OVERDISTRIB-NII-PRIOR> (194450)
<OVERDIST-NET-GAINS-PRIOR> (153792985)
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<PER-SHARE-NAV-BEGIN> 8.06
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<PER-SHARE-DIVIDEND> (0.26)
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<EXPENSE-RATIO> 0.79
</TABLE>
