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SIGNATURE JAMES O. YOST
TITLE ASSISTANT TREASURER
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<REALIZED-GAINS-CURRENT> (30170435)
<APPREC-INCREASE-CURRENT> 97361506
<NET-CHANGE-FROM-OPS> 142937006
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 756472
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 4854733
<NUMBER-OF-SHARES-REDEEMED> 2541586
<SHARES-REINVESTED> 87659
<NET-CHANGE-IN-ASSETS> 106935725
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (243352041)
<OVERDISTRIB-NII-PRIOR> 1399154
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 4031708
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 11412909
<AVERAGE-NET-ASSETS> 886159671
<PER-SHARE-NAV-BEGIN> 4.85
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<PER-SHARE-DIVIDEND> 0.40
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<PER-SHARE-NAV-END> 5.25
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<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY INFORMATION EXTRACTED FROM THE FINANCIAL
STATEMENTS OF MFS MUNICIPAL HIGH INCOME FUND CLASS A AND IS QUALIFIED IN ITS
ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000225604
<NAME> MFS SERIES TRUST III
<SERIES>
<NUMBER> 021
<NAME> MFS MUNICIPAL HIGH INCOME FUND CLASS A
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JAN-31-1996
<PERIOD-END> JAN-31-1996
<INVESTMENTS-AT-COST> 1007461049
<INVESTMENTS-AT-VALUE> 1075759250
<RECEIVABLES> 20369316
<ASSETS-OTHER> 13097
<OTHER-ITEMS-ASSETS> 738588
<TOTAL-ASSETS> 1096880251
<PAYABLE-FOR-SECURITIES> 5159564
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4881656
<TOTAL-LIABILITIES> 10041220
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1124411855
<SHARES-COMMON-STOCK> 110653810
<SHARES-COMMON-PRIOR> 107020050
<ACCUMULATED-NII-CURRENT> 3005866
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> 8876891
<ACCUM-APPREC-OR-DEPREC> 68298201
<NET-ASSETS> 1086839031
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 81329990
<OTHER-INCOME> 0
<EXPENSES-NET> 10284695
<NET-INVESTMENT-INCOME> 71045295
<REALIZED-GAINS-CURRENT> (24859595)
<APPREC-INCREASE-CURRENT> 88864128
<NET-CHANGE-FROM-OPS> 135049828
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 69946556
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 15092575
<NUMBER-OF-SHARES-REDEEMED> 14380028
<SHARES-REINVESTED> 2921213
<NET-CHANGE-IN-ASSETS> 111121184
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (84017296)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 6996766
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 10429436
<AVERAGE-NET-ASSETS> 1049952524
<PER-SHARE-NAV-BEGIN> 8.60
<PER-SHARE-NII> 0.61
<PER-SHARE-GAIN-APPREC> 0.59
<PER-SHARE-DIVIDEND> 0.68
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0.00
<PER-SHARE-NAV-END> 9.12
<EXPENSE-RATIO> 0.93
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY INFORMATION EXTRACTED FROM THE FINANCIAL
STATEMENTS OF MFS SERIES MFS MUNICIPAL HIGH INCOME FUND CLASS B AND IS QUALIFIED
IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000225604
<NAME> MFS SERIES TRUST III
<SERIES>
<NUMBER> 022
<NAME> MFS MUNICIPAL HIGH INCOME FUND CLASS B
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JAN-31-1996
<PERIOD-END> JAN-31-1996
<INVESTMENTS-AT-COST> 1007461049
<INVESTMENTS-AT-VALUE> 1075759250
<RECEIVABLES> 20369316
<ASSETS-OTHER> 13097
<OTHER-ITEMS-ASSETS> 738588
<TOTAL-ASSETS> 1096880251
<PAYABLE-FOR-SECURITIES> 5159564
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4881656
<TOTAL-LIABILITIES> 10041220
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1124411855
<SHARES-COMMON-STOCK> 8531656
<SHARES-COMMON-PRIOR> 6476558
<ACCUMULATED-NII-CURRENT> 3005866
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> 8876891
<ACCUM-APPREC-OR-DEPREC> 68298201
<NET-ASSETS> 1086839031
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 81329990
<OTHER-INCOME> 0
<EXPENSES-NET> 10284695
<NET-INVESTMENT-INCOME> 71045295
<REALIZED-GAINS-CURRENT> (24859595)
<APPREC-INCREASE-CURRENT> 88864128
<NET-CHANGE-FROM-OPS> 135049828
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 4150972
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 2715689
<NUMBER-OF-SHARES-REDEEMED> 856621
<SHARES-REINVESTED> 196030
<NET-CHANGE-IN-ASSETS> 111121184
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (84017296)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 6996766
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 10429436
<AVERAGE-NET-ASSETS> 1049952524
<PER-SHARE-NAV-BEGIN> 8.60
<PER-SHARE-NII> 0.52
<PER-SHARE-GAIN-APPREC> 0.59
<PER-SHARE-DIVIDEND> 0.59
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0.00
<PER-SHARE-NAV-END> 9.12
<EXPENSE-RATIO> 1.91
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
