<PAGE> PAGE 1
000 B000000 01/31/97
000 C000000 0000225604
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 3.0.a
000 J000000 A
001 A000000 MFS SERIES TRUST III
001 B000000 811-2794
001 C000000 6179545000
002 A000000 500 BOYLSTON STREET
002 B000000 BOSTON
002 C000000 MA
002 D010000 02116
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 Y
007 B000000 2
007 C010100 1
007 C020100 MFS HIGH INCOME FUND
007 C030100 N
007 C010200 2
007 C020200 MFS MUNICIPAL HIGH INCOME FUND
007 C030200 N
007 C010300 3
007 C010400 4
007 C010500 5
007 C010600 6
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
008 A00AA01 MASSACHUSETTS FINANCIAL SERVICE COMPANY
008 B00AA01 A
008 C00AA01 801-17352
008 D01AA01 BOSTON
008 D02AA01 MA
008 D03AA01 02116
011 A00AA01 MFS FUND DISTRIBUTORS, INC.
011 B00AA01 8-27864
011 C01AA01 BOSTON
011 C02AA01 MA
011 C03AA01 02116
012 A00AA01 MFS SERVICE CENTER, INC.
012 B00AA01 84-1316
012 C01AA01 BOSTON
012 C02AA01 MA
<PAGE> PAGE 2
012 C03AA01 02116
018 00AA00 Y
019 A00AA00 Y
019 B00AA00 53
019 C00AA00 MASSFINSER
020 C000001 0
020 C000002 0
020 C000003 0
020 C000004 0
020 C000005 0
020 C000006 0
020 C000007 0
020 C000008 0
020 C000009 0
020 C000010 0
021 000000 0
022 A000001 GENERAL ELECTRIC CAP CORP.
022 B000001 00-0000000
022 C000001 730541
022 D000001 0
022 A000002 CS FIRST BOSTON CORP.
022 B000002 13-5659485
022 C000002 234689
022 D000002 21635
022 A000003 DLJ FIXED INCOME
022 B000003 13-2741729
022 C000003 148961
022 D000003 88987
022 A000004 MORGAN STANLEY
022 B000004 13-2655998
022 C000004 105077
022 D000004 124497
022 A000005 PAIN WEBBER
022 B000005 13-2638166
022 C000005 119680
022 D000005 108601
022 A000006 MORGAN (J.P.) SECURITIES
022 B000006 13-3224016
022 C000006 131036
022 D000006 39005
022 A000007 CHASE SECURITIES
022 B000007 13-3112953
022 C000007 169016
022 D000007 0
022 A000008 PRUDENTIAL SECURITIES
022 B000008 11226938-1
022 C000008 112269
022 D000008 42474
022 A000009 CARROL MCENTEE
022 B000009 00-0000000
022 C000009 113157
<PAGE> PAGE 3
022 D000009 37543
022 A000010 LEHMAN BROTHERS
022 B000010 13-2518466
022 C000010 45051
022 D000010 25373
023 C000000 3211997
023 D000000 1237185
025 D00AA01 0
025 D00AA02 0
025 D00AA03 0
025 D00AA04 0
025 D00AA05 0
025 D00AA06 0
025 D00AA07 0
025 D00AA08 0
026 A000000 Y
026 B000000 Y
026 C000000 N
026 D000000 Y
026 E000000 N
026 F000000 N
026 G010000 N
026 G020000 N
026 H000000 N
027 000000 Y
054 A00AA00 Y
054 B00AA00 Y
054 C00AA00 N
054 D00AA00 N
054 E00AA00 N
054 F00AA00 N
054 G00AA00 N
054 H00AA00 Y
054 I00AA00 N
054 J00AA00 Y
054 K00AA00 N
054 L00AA00 N
054 M00AA00 Y
054 N00AA00 N
054 O00AA00 N
066 A00AA00 N
067 00AA00 N
068 A00AA00 N
068 B00AA00 N
069 00AA00 N
077 A000000 Y
077 D000000 Y
077 I000000 Y
077 Q010000 Y
078 000000 N
080 A00AA00 NATIONAL UNION INSURANCE CO.
<PAGE> PAGE 4
080 B00AA00 ICI MUTUAL
080 C00AA00 75000
081 A00AA00 Y
081 B00AA00 116
082 A00AA00 Y
082 B00AA00 100
083 A00AA00 N
083 B00AA00 0
084 A00AA00 N
084 B00AA00 0
085 A00AA00 Y
085 B00AA00 N
086 A010000 0
086 A020000 0
086 B010000 0
086 B020000 0
086 C010000 0
086 C020000 0
086 D010000 0
086 D020000 0
086 E010000 0
086 E020000 0
086 F010000 0
086 F020000 0
013 A000101 DELOITTE & TOUCHE LLP
013 B010101 BOSTON
013 B020101 MA
013 B030101 02110
015 A000101 STATE STREET BANK AND TRUST COMPANY
015 B000101 C
015 C010101 BOSTON
015 C020101 MA
015 C030101 02110
015 E010101 X
015 A000102 CHASE MANHATTAN BANK, N.A.
015 B000102 S
015 C010102 NEW YORK
015 C020102 NY
015 C030102 10081
015 E040102 X
015 A000103 THE BANK OF NEW YORK
015 B000103 S
015 C010103 NEW YORK
015 C020103 NY
015 C030103 10286
015 E010103 X
024 000100 N
028 A010100 36371
028 A020100 3926
028 A030100 0
028 A040100 18966
<PAGE> PAGE 5
028 B010100 30829
028 B020100 4011
028 B030100 0
028 B040100 16286
028 C010100 32145
028 C020100 3765
028 C030100 0
028 C040100 67582
028 D010100 32076
028 D020100 3876
028 D030100 0
028 D040100 17722
028 E010100 47069
028 E020100 4057
028 E030100 0
028 E040100 26213
028 F010100 61677
028 F020100 4024
028 F030100 0
028 F040100 57905
028 G010100 240167
028 G020100 23659
028 G030100 0
028 G040100 204673
028 H000100 130098
029 000100 Y
030 A000100 1125
030 B000100 4.75
030 C000100 0.00
031 A000100 193
031 B000100 0
032 000100 931
033 000100 0
034 000100 Y
035 000100 470
036 A000100 N
036 B000100 0
037 000100 N
038 000100 0
039 000100 N
040 000100 Y
041 000100 Y
042 A000100 0
042 B000100 0
042 C000100 51
042 D000100 49
042 E000100 0
042 F000100 0
042 G000100 0
042 H000100 0
043 000100 4851
<PAGE> PAGE 6
044 000100 0
045 000100 Y
046 000100 N
047 000100 N
048 000100 0.000
048 A010100 0
048 A020100 0.000
048 B010100 0
048 B020100 0.000
048 C010100 0
048 C020100 0.000
048 D010100 0
048 D020100 0.000
048 E010100 0
048 E020100 0.000
048 F010100 0
048 F020100 0.000
048 G010100 0
048 G020100 0.000
048 H010100 0
048 H020100 0.000
048 I010100 0
048 I020100 0.000
048 J010100 0
048 J020100 0.000
048 K010100 0
048 K020100 0.000
049 000100 N
050 000100 Y
051 000100 N
052 000100 N
053 A000100 Y
053 B000100 N
053 C000100 Y
055 A000100 Y
055 B000100 N
056 000100 Y
057 000100 N
058 A000100 N
059 000100 Y
060 A000100 Y
060 B000100 Y
061 000100 1000
062 A000100 Y
062 B000100 0.0
062 C000100 2.9
062 D000100 0.0
062 E000100 0.0
062 F000100 0.0
062 G000100 0.0
062 H000100 0.0
<PAGE> PAGE 7
062 I000100 0.0
062 J000100 0.0
062 K000100 0.0
062 L000100 0.0
062 M000100 0.0
062 N000100 0.0
062 O000100 0.0
062 P000100 87.8
062 Q000100 0.0
062 R000100 6.2
063 A000100 0
063 B000100 8.0
064 A000100 N
064 B000100 N
070 A010100 Y
070 A020100 N
070 B010100 N
070 B020100 N
070 C010100 Y
070 C020100 N
070 D010100 N
070 D020100 N
070 E010100 Y
070 E020100 N
070 F010100 N
070 F020100 N
070 G010100 Y
070 G020100 N
070 H010100 N
070 H020100 N
070 I010100 N
070 I020100 N
070 J010100 Y
070 J020100 Y
070 K010100 Y
070 K020100 N
070 L010100 Y
070 L020100 Y
070 M010100 Y
070 M020100 N
070 N010100 Y
070 N020100 N
070 O010100 Y
070 O020100 N
070 P010100 Y
070 P020100 N
070 Q010100 N
070 Q020100 N
070 R010100 N
070 R020100 N
071 A000100 829161
<PAGE> PAGE 8
071 B000100 768213
071 C000100 881896
071 D000100 87
072 A000100 12
072 B000100 91866
072 C000100 136
072 D000100 0
072 E000100 0
072 F000100 4238
072 G000100 0
072 H000100 0
072 I000100 1527
072 J000100 331
072 K000100 172
072 L000100 45
072 M000100 51
072 N000100 0
072 O000100 0
072 P000100 0
072 Q000100 0
072 R000100 56
072 S000100 2
072 T000100 4930
072 U000100 0
072 V000100 0
072 W000100 486
072 X000100 11838
072 Y000100 255
072 Z000100 80419
072AA000100 1478
072BB000100 0
072CC010100 18446
072CC020100 0
072DD010100 54869
072DD020100 23285
072EE000100 0
073 A010100 0.4600
073 A020100 0.4200
073 B000100 0.0000
073 C000100 0.0000
074 A000100 36
074 B000100 0
074 C000100 29312
074 D000100 881581
074 E000100 53343
074 F000100 8335
074 G000100 0
074 H000100 0
074 I000100 469
074 J000100 18113
074 K000100 0
<PAGE> PAGE 9
074 L000100 28689
074 M000100 10
074 N000100 1019888
074 O000100 11247
074 P000100 16
074 Q000100 0
074 R010100 0
074 R020100 0
074 R030100 0
074 R040100 4327
074 S000100 0
074 T000100 1004298
074 U010100 125639
074 U020100 56216
074 V010100 5.35
074 V020100 5.35
074 W000100 0.0000
074 X000100 47669
074 Y000100 0
075 A000100 0
075 B000100 928526
076 000100 0.00
013 A000201 ERNST & YOUNG LLP
013 B010201 BOSTON
013 B020201 MA
013 B030201 02116
015 A000201 STATE STREET BANK AND TRUST COMPANY
015 B000201 C
015 C010201 BOSTON
015 C020201 MA
015 C030201 02110
015 E010201 X
015 A000202 THE BANK OF NEW YORK
015 B000202 S
015 C010202 NEW YORK
015 C020202 NY
015 C030202 10286
015 E010202 X
015 A000203 CHEMICAL BANK
015 B000203 S
015 C010203 NEW YORK
015 C020203 NY
015 C030203 10041
015 E010203 X
015 A000204 MORGAN GUARANTY TRUST COMPANY
015 B000204 S
015 C010204 NEW YORK
015 C020204 NY
015 C030204 10015
015 E010204 X
015 A000205 BANKERS TRUST COMPANY
<PAGE> PAGE 10
015 B000205 S
015 C010205 NEW YORK
015 C020205 NY
015 C030205 10015
015 E010205 X
024 000200 N
028 A010200 37155
028 A020200 2047
028 A030200 0
028 A040200 10581
028 B010200 19817
028 B020200 4340
028 B030200 0
028 B040200 12292
028 C010200 25730
028 C020200 2153
028 C030200 0
028 C040200 12169
028 D010200 25751
028 D020200 2201
028 D030200 0
028 D040200 9855
028 E010200 23211
028 E020200 2221
028 E030200 0
028 E040200 20305
028 F010200 30722
028 F020200 2227
028 F030200 0
028 F040200 16852
028 G010200 162386
028 G020200 15189
028 G030200 0
028 G040200 82053
028 H000200 109206
029 000200 Y
030 A000200 3806
030 B000200 4.75
030 C000200 0.00
031 A000200 667
031 B000200 0
032 000200 3139
033 000200 0
034 000200 Y
035 000200 214
036 A000200 N
036 B000200 0
037 000200 N
038 000200 0
039 000200 N
040 000200 Y
<PAGE> PAGE 11
041 000200 Y
042 A000200 0
042 B000200 0
042 C000200 88
042 D000200 12
042 E000200 0
042 F000200 0
042 G000200 0
042 H000200 0
043 000200 767
044 000200 0
045 000200 Y
046 000200 N
047 000200 N
048 000200 0.000
048 A010200 0
048 A020200 0.000
048 B010200 0
048 B020200 0.000
048 C010200 0
048 C020200 0.000
048 D010200 0
048 D020200 0.000
048 E010200 0
048 E020200 0.000
048 F010200 0
048 F020200 0.000
048 G010200 0
048 G020200 0.000
048 H010200 0
048 H020200 0.000
048 I010200 0
048 I020200 0.000
048 J010200 0
048 J020200 0.000
048 K010200 0
048 K020200 0.000
049 000200 N
050 000200 Y
051 000200 N
052 000200 N
053 A000200 Y
053 B000200 N
053 C000200 Y
055 A000200 N
055 B000200 N
056 000200 Y
057 000200 N
058 A000200 N
059 000200 Y
060 A000200 N
<PAGE> PAGE 12
060 B000200 N
061 000200 1000
062 A000200 Y
062 B000200 0.0
062 C000200 0.0
062 D000200 0.0
062 E000200 0.0
062 F000200 0.0
062 G000200 0.0
062 H000200 0.0
062 I000200 0.0
062 J000200 0.0
062 K000200 0.0
062 L000200 1.8
062 M000200 0.0
062 N000200 0.0
062 O000200 98.0
062 P000200 0.0
062 Q000200 0.0
062 R000200 0.0
063 A000200 0
063 B000200 20.3
064 A000200 Y
064 B000200 Y
065 000200 N
070 A010200 Y
070 A020200 N
070 B010200 N
070 B020200 N
070 C010200 Y
070 C020200 N
070 D010200 N
070 D020200 N
070 E010200 Y
070 E020200 N
070 F010200 N
070 F020200 N
070 G010200 Y
070 G020200 N
070 H010200 N
070 H020200 N
070 I010200 N
070 I020200 N
070 J010200 Y
070 J020200 Y
070 K010200 Y
070 K020200 N
070 L010200 N
070 L020200 N
070 M010200 N
070 M020200 N
<PAGE> PAGE 13
070 N010200 Y
070 N020200 N
070 O010200 Y
070 O020200 N
070 P010200 Y
070 P020200 N
070 Q010200 N
070 Q020200 N
070 R010200 N
070 R020200 N
071 A000200 226617
071 B000200 176782
071 C000200 1047482
071 D000200 17
072 A000200 12
072 B000200 83622
072 C000200 0
072 D000200 0
072 E000200 0
072 F000200 7154
072 G000200 0
072 H000200 0
072 I000200 1500
072 J000200 373
072 K000200 117
072 L000200 69
072 M000200 61
072 N000200 0
072 O000200 0
072 P000200 0
072 Q000200 0
072 R000200 36
072 S000200 28
072 T000200 774
072 U000200 0
072 V000200 0
072 W000200 631
072 X000200 10743
072 Y000200 137
072 Z000200 73017
072AA000200 0
072BB000200 22959
072CC010200 0
072CC020200 20906
072DD010200 70124
072DD020200 5580
072EE000200 0
073 A010200 0.6400
073 A020200 0.5500
073 B000200 0.0000
073 C000200 0.0000
<PAGE> PAGE 14
074 A000200 39
074 B000200 0
074 C000200 19950
074 D000200 1092180
074 E000200 0
074 F000200 0
074 G000200 0
074 H000200 0
074 I000200 0
074 J000200 2529
074 K000200 0
074 L000200 21803
074 M000200 12
074 N000200 1136513
074 O000200 13040
074 P000200 26
074 Q000200 0
074 R010200 0
074 R020200 0
074 R030200 0
074 R040200 9299
074 S000200 0
074 T000200 1114148
074 U010200 113149
074 U020200 14412
074 V010200 8.73
074 V020200 8.74
074 W000200 0.0000
074 X000200 31412
074 Y000200 0
075 A000200 0
075 B000200 1061134
076 000200 0.00
SIGNATURE JAMES O. YOST
TITLE ASSISTANT TREASURER
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000225604
<NAME> MFS SERIES TRUST III
<SERIES>
<NUMBER> 011
<NAME> MFS HIGH INCOME FUND CLASS A
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> JAN-31-1997
<PERIOD-START> FEB-01-1996
<PERIOD-END> JAN-31-1997
<INVESTMENTS-AT-COST> 947505015
<INVESTMENTS-AT-VALUE> 973040069
<RECEIVABLES> 46801726
<ASSETS-OTHER> 9602
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 1019887604
<PAYABLE-FOR-SECURITIES> 11246809
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4343437
<TOTAL-LIABILITIES> 15590246
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1251191564
<SHARES-COMMON-STOCK> 125638629
<SHARES-COMMON-PRIOR> 118365548
<ACCUMULATED-NII-CURRENT> 1677232
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (274106492)
<ACCUM-APPREC-OR-DEPREC> 25535054
<NET-ASSETS> 1004297358
<DIVIDEND-INCOME> 135769
<INTEREST-INCOME> 91865911
<OTHER-INCOME> 0
<EXPENSES-NET> 11583070
<NET-INVESTMENT-INCOME> 80418610
<REALIZED-GAINS-CURRENT> 1477653
<APPREC-INCREASE-CURRENT> 18445626
<NET-CHANGE-FROM-OPS> 100341889
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 54869246
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 52421821
<NUMBER-OF-SHARES-REDEEMED> (51220588)
<SHARES-REINVESTED> 6071848
<NET-CHANGE-IN-ASSETS> 84509161
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> (2736501)
<OVERDIST-NET-GAINS-PRIOR> (271652470)
<GROSS-ADVISORY-FEES> 4238339
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 11837656
<AVERAGE-NET-ASSETS> 928526080
<PER-SHARE-NAV-BEGIN> 5.24
<PER-SHARE-NII> 0.47
<PER-SHARE-GAIN-APPREC> 0.10
<PER-SHARE-DIVIDEND> (0.46)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 5.35
<EXPENSE-RATIO> 1.02
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000225604
<NAME> MFS SERIES TRUST III
<SERIES>
<NUMBER> 012
<NAME> MFS HIGH INCOME FUND CLASS B
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> JAN-31-1997
<PERIOD-START> FEB-01-1996
<PERIOD-END> JAN-31-1997
<INVESTMENTS-AT-COST> 947505015
<INVESTMENTS-AT-VALUE> 973040069
<RECEIVABLES> 46801726
<ASSETS-OTHER> 9602
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 1019887604
<PAYABLE-FOR-SECURITIES> 11246809
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4343437
<TOTAL-LIABILITIES> 15590246
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1251191564
<SHARES-COMMON-STOCK> 56215947
<SHARES-COMMON-PRIOR> 54039504
<ACCUMULATED-NII-CURRENT> 1677232
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (274106492)
<ACCUM-APPREC-OR-DEPREC> 25535054
<NET-ASSETS> 1004297358
<DIVIDEND-INCOME> 135769
<INTEREST-INCOME> 91865911
<OTHER-INCOME> 0
<EXPENSES-NET> 11583070
<NET-INVESTMENT-INCOME> 80418610
<REALIZED-GAINS-CURRENT> 1477653
<APPREC-INCREASE-CURRENT> 18445626
<NET-CHANGE-FROM-OPS> 100341889
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 23285081
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 35443924
<NUMBER-OF-SHARES-REDEEMED> (35539089)
<SHARES-REINVESTED> 2271608
<NET-CHANGE-IN-ASSETS> 84509161
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> (2736501)
<OVERDIST-NET-GAINS-PRIOR> (271652470)
<GROSS-ADVISORY-FEES> 4238339
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 11837656
<AVERAGE-NET-ASSETS> 928526080
<PER-SHARE-NAV-BEGIN> 5.24
<PER-SHARE-NII> 0.43
<PER-SHARE-GAIN-APPREC> 0.10
<PER-SHARE-DIVIDEND> (0.42)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 5.35
<EXPENSE-RATIO> 1.79
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000225604
<NAME> SERIES TRUST III
<SERIES>
<NUMBER> 013
<NAME> MFS HIGH INCOME FUND CLASS C
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> JAN-31-1997
<PERIOD-START> FEB-01-1996
<PERIOD-END> JAN-31-1997
<INVESTMENTS-AT-COST> 947505015
<INVESTMENTS-AT-VALUE> 973040069
<RECEIVABLES> 46801726
<ASSETS-OTHER> 9602
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 1019887604
<PAYABLE-FOR-SECURITIES> 11246809
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4343437
<TOTAL-LIABILITIES> 15590246
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1251191564
<SHARES-COMMON-STOCK> 5265960
<SHARES-COMMON-PRIOR> 3107032
<ACCUMULATED-NII-CURRENT> 1677232
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (274106492)
<ACCUM-APPREC-OR-DEPREC> 25535054
<NET-ASSETS> 1004297358
<DIVIDEND-INCOME> 135769
<INTEREST-INCOME> 91865911
<OTHER-INCOME> 0
<EXPENSES-NET> 11583070
<NET-INVESTMENT-INCOME> 80418610
<REALIZED-GAINS-CURRENT> 1477653
<APPREC-INCREASE-CURRENT> 18445626
<NET-CHANGE-FROM-OPS> 100341889
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 1760418
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 4433093
<NUMBER-OF-SHARES-REDEEMED> (2477675)
<SHARES-REINVESTED> 203510
<NET-CHANGE-IN-ASSETS> 84509161
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> (2736501)
<OVERDIST-NET-GAINS-PRIOR> (271652470)
<GROSS-ADVISORY-FEES> 4238339
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 11837656
<AVERAGE-NET-ASSETS> 928526080
<PER-SHARE-NAV-BEGIN> 5.25
<PER-SHARE-NII> 0.43
<PER-SHARE-GAIN-APPREC> 0.11
<PER-SHARE-DIVIDEND> (0.43)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 5.36
<EXPENSE-RATIO> 1.72
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000225604
<NAME> MFS SERIES TRUST III
<SERIES>
<NUMBER> 014
<NAME> MFS HIGH INCOME FUND CLASS I
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> JAN-31-1997
<PERIOD-START> FEB-01-1996
<PERIOD-END> JAN-31-1997
<INVESTMENTS-AT-COST> 947505015
<INVESTMENTS-AT-VALUE> 973040069
<RECEIVABLES> 46801726
<ASSETS-OTHER> 9602
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 1019887604
<PAYABLE-FOR-SECURITIES> 11246809
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4343437
<TOTAL-LIABILITIES> 15590246
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1251191564
<SHARES-COMMON-STOCK> 572355
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 1677232
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (274106492)
<ACCUM-APPREC-OR-DEPREC> 25535054
<NET-ASSETS> 1004297358
<DIVIDEND-INCOME> 135769
<INTEREST-INCOME> 91865911
<OTHER-INCOME> 0
<EXPENSES-NET> 11583070
<NET-INVESTMENT-INCOME> 80418610
<REALIZED-GAINS-CURRENT> 1477653
<APPREC-INCREASE-CURRENT> 18445626
<NET-CHANGE-FROM-OPS> 100341889
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (21807)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 568279
<NUMBER-OF-SHARES-REDEEMED> 0
<SHARES-REINVESTED> 4076
<NET-CHANGE-IN-ASSETS> 84509161
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> (2736501)
<OVERDIST-NET-GAINS-PRIOR> (271652470)
<GROSS-ADVISORY-FEES> 4238339
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 11837656
<AVERAGE-NET-ASSETS> 928526080
<PER-SHARE-NAV-BEGIN> 5.34
<PER-SHARE-NII> 0.04
<PER-SHARE-GAIN-APPREC> 0.01
<PER-SHARE-DIVIDEND> (0.04)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 5.35
<EXPENSE-RATIO> 0.59
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000225604
<NAME> MFS SERIES TUST III
<SERIES>
<NUMBER> 011
<NAME> MUNICIPAL HIGH INCOME FUND CLASS A
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JAN-31-1997
<PERIOD-START> FEB-01-1996
<PERIOD-END> JAN-31-1997
<INVESTMENTS-AT-COST> 1064738280
<INVESTMENTS-AT-VALUE> 10112130260
<RECEIVABLES> 24332113
<ASSETS-OTHER> 11653
<OTHER-ITEMS-ASSETS> 39399
<TOTAL-ASSETS> 1136513425
<PAYABLE-FOR-SECURITIES> 13039959
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 9324949
<TOTAL-LIABILITIES> 22364908
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1197896807
<SHARES-COMMON-STOCK> 113148629
<SHARES-COMMON-PRIOR> 110653810
<ACCUMULATED-NII-CURRENT> 618295
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (131758656)
<ACCUM-APPREC-OR-DEPREC> 47391980
<NET-ASSETS> 1114148517
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 83622285
<OTHER-INCOME> 0
<EXPENSES-NET> 10605424
<NET-INVESTMENT-INCOME> 73016861
<REALIZED-GAINS-CURRENT> (22959311)
<APPREC-INCREASE-CURRENT> (20906221)
<NET-CHANGE-FROM-OPS> 29151329
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (70123751)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 16594610
<NUMBER-OF-SHARES-REDEEMED> (17043700)
<SHARES-REINVESTED> 2943909
<NET-CHANGE-IN-ASSETS> 27309486
<ACCUMULATED-NII-PRIOR> 3005866
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> (108876891)
<GROSS-ADVISORY-FEES> 7154011
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 10742920
<AVERAGE-NET-ASSETS> 1061134288
<PER-SHARE-NAV-BEGIN> 9.12
<PER-SHARE-NII> 0.61
<PER-SHARE-GAIN-APPREC> (0.36)
<PER-SHARE-DIVIDEND> (0.64)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 8.73
<EXPENSE-RATIO> 0.93
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000225604
<NAME> MFS SERIES TRUST III
<SERIES>
<NUMBER> 012
<NAME> MUNICIPAL HIGH INCOME FUND CLASS B
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JAN-31-1997
<PERIOD-START> FEB-01-1996
<PERIOD-END> JAN-31-1997
<INVESTMENTS-AT-COST> 1064738280
<INVESTMENTS-AT-VALUE> 10112130260
<RECEIVABLES> 24332113
<ASSETS-OTHER> 11653
<OTHER-ITEMS-ASSETS> 39399
<TOTAL-ASSETS> 1136513425
<PAYABLE-FOR-SECURITIES> 13039959
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 9324949
<TOTAL-LIABILITIES> 22364908
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1197896807
<SHARES-COMMON-STOCK> 14411582
<SHARES-COMMON-PRIOR> 8531656
<ACCUMULATED-NII-CURRENT> 618295
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (131758656)
<ACCUM-APPREC-OR-DEPREC> 47391980
<NET-ASSETS> 1114148517
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 83622285
<OTHER-INCOME> 0
<EXPENSES-NET> 10605424
<NET-INVESTMENT-INCOME> 73016861
<REALIZED-GAINS-CURRENT> (22959311)
<APPREC-INCREASE-CURRENT> (20906221)
<NET-CHANGE-FROM-OPS> 29151329
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (5579841)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 6763017
<NUMBER-OF-SHARES-REDEEMED> (1121560)
<SHARES-REINVESTED> 238469
<NET-CHANGE-IN-ASSETS> 27309486
<ACCUMULATED-NII-PRIOR> 3005866
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> (108876891)
<GROSS-ADVISORY-FEES> 7154011
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 10742920
<AVERAGE-NET-ASSETS> 1061134288
<PER-SHARE-NAV-BEGIN> 9.12
<PER-SHARE-NII> 0.52
<PER-SHARE-GAIN-APPREC> (0.35)
<PER-SHARE-DIVIDEND> (0.55)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 8.74
<EXPENSE-RATIO> 1.86
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
