<PAGE> PAGE 1
000 B000000 07/31/1999
000 C000000 0000783740
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 6.1
000 J000000 A
001 A000000 MFS SERIES TRUST X
001 B000000 811-4492
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 4
007 C010100 1
007 C020100 MFS GOVERNMENT MORTGAGE FUND
007 C030100 N
007 C010200 2
007 C020200 MFS EMERGING MARKETS DEBT FUND
007 C030200 N
007 C010300 3
007 C020300 MFS SMALL CAP VALUE FUND
007 C030300 N
007 C010400 4
007 C020400 MFS STRATEGIC VALUE FUND
007 C030400 N
007 C010500 5
007 C010600 6
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
008 A00AA01 MASSACHUSETTS FINANCIAL SERVICES COMPANY
008 B00AA01 A
008 C00AA01 801-17352
008 D01AA01 BOSTON
008 D02AA01 MA
008 D03AA01 02116
010 A00AA01 MASSACHUSETTS FINANCIAL SERVICES COMPANY
010 B00AA01 801-17352
010 C01AA01 BOSTON
010 C02AA01 MA
010 C03AA01 02116
<PAGE> PAGE 2
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
012 C03AA01 02116
015 A00AA01 STATE STREET BANK AND TRUST COMPANY
015 B00AA01 C
015 C01AA01 BOSTON
015 C02AA01 MA
015 C03AA01 02110
015 E01AA01 X
015 A00AA02 STATE STREET BANK AND TRUST COMPANY
015 B00AA02 S
015 C01AA02 BOSTON
015 C02AA02 MA
015 C03AA02 02110
015 E04AA02 X
015 A00AA03 THE BANK OF NEW YORK
015 B00AA03 S
015 C01AA03 NEW YORK
015 C02AA03 NY
015 C03AA03 10286
015 E01AA03 X
018 00AA00 Y
019 A00AA00 Y
019 B00AA00 53
019 C00AA00 MASSFINSER
020 A000001 INSTINET
020 B000001 13-3443395
020 C000001 1
020 A000002 DUNLEVY & CO, INC.
020 B000002 00-0000000
020 C000002 1
020 A000003 DONALDSON, LUFKIN, & JENRE
020 B000003 13-2741729
020 C000003 0
020 A000004 NATIONAL FINANCIAL SERVICES
020 B000004 00-0000000
020 C000004 0
020 A000005 MERRILL LYNCH PIERCE FENN
020 B000005 13-5674085
020 C000005 0
020 A000006 SALOMON SMITH BARNEY INC.
020 B000006 13-3082694
020 C000006 0
020 A000007 MORGAN STANLEY AND CO., INC.
<PAGE> PAGE 3
020 B000007 13-2655998
020 C000007 0
020 A000008 GOLDMAN SACHS & CO.
020 B000008 13-5108880
020 C000008 0
020 A000009 JONES & ASSOCIATES
020 B000009 00-0000000
020 C000009 0
020 A000010 CS FIRST BOSTON CORP.
020 B000010 13-5659485
020 C000010 0
021 000000 5
022 A000001 GOLDMAN SACHS & CO.
022 B000001 13-5108880
022 C000001 11380636
022 D000001 349009
022 A000002 SALOMON SMITH BARNEY
022 B000002 13-3082694
022 C000002 246738
022 D000002 137611
022 A000003 MERRILL LYNCH
022 B000003 13-5674085
022 C000003 235422
022 D000003 213371
022 A000004 LEHMAN BROS INC.
022 B000004 13-2518466
022 C000004 174651
022 D000004 182882
022 A000005 PAINE WEBBER
022 B000005 13-2638166
022 C000005 130353
022 D000005 128236
022 A000006 DEUTSCHE BANK SECURITIES
022 B000006 13-2730828
022 C000006 88016
022 D000006 97676
022 A000007 BANK BOSTON
022 B000007 00-0000000
022 C000007 81843
022 D000007 132
022 A000008 BANK OF AMERICA
022 B000008 94-1687665
022 C000008 69521
022 D000008 0
022 A000009 CS FIRST BOSTON
022 B000009 13-5659485
022 C000009 21594
022 D000009 45434
022 A000010 BEAR STEARNS SECURITIES
022 B000010 13-3299429
022 C000010 20216
<PAGE> PAGE 4
022 D000010 66315
023 C000000 12527142
023 D000000 1233790
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
037 00AA00 N
038 00AA00 0
039 00AA00 N
040 00AA00 Y
041 00AA00 Y
054 A00AA00 Y
054 B00AA00 N
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
077 A000000 Y
077 B000000 Y
077 H000000 Y
077 Q010000 Y
078 000000 N
080 A00AA00 NATIONAL UNION/CHUBB
080 B00AA00 FEDERAL INSURANCE
080 C00AA00 80
081 A00AA00 Y
081 B00AA00 133
082 A00AA00 Y
082 B00AA00 100
083 A00AA00 N
083 B00AA00 0
084 A00AA00 N
084 B00AA00 0
085 A00AA00 Y
085 B00AA00 N
<PAGE> PAGE 5
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 02116
024 000100 Y
025 A000101 GOLDMAN SACHS
025 B000101 13-5108880
025 C000101 D
025 D000101 3606
025 D000102 0
025 D000103 0
025 D000104 0
025 D000105 0
025 D000106 0
025 D000107 0
025 D000108 0
028 A010100 11534
028 A020100 1815
028 A030100 0
028 A040100 17465
028 B010100 15481
028 B020100 1818
028 B030100 0
028 B040100 26610
028 C010100 12625
028 C020100 1803
028 C030100 0
028 C040100 22220
028 D010100 37564
028 D020100 1801
028 D030100 0
028 D040100 50648
028 E010100 31807
028 E020100 1827
028 E030100 0
028 E040100 41511
028 F010100 7480
028 F020100 1769
028 F030100 0
<PAGE> PAGE 6
028 F040100 16092
028 G010100 116491
028 G020100 10833
028 G030100 0
028 G040100 174546
028 H000100 110936
029 000100 Y
030 A000100 270
030 B000100 4.75
030 C000100 0.00
031 A000100 43
031 B000100 0
032 000100 227
033 000100 0
034 000100 Y
035 000100 98
036 A000100 N
036 B000100 0
042 A000100 0
042 B000100 0
042 C000100 33
042 D000100 67
042 E000100 0
042 F000100 0
042 G000100 0
042 H000100 0
043 000100 2901
044 000100 0
045 000100 Y
046 000100 N
047 000100 Y
048 000100 0.450
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
<PAGE> PAGE 7
048 J020100 0.000
048 K010100 0
048 K020100 0.000
049 000100 N
050 000100 N
051 000100 N
052 000100 N
053 A000100 Y
053 B000100 Y
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 0.0
062 D000100 0.5
062 E000100 0.0
062 F000100 0.0
062 G000100 0.0
062 H000100 0.0
062 I000100 0.0
062 J000100 0.0
062 K000100 0.0
062 L000100 0.0
062 M000100 4.4
062 N000100 94.6
062 O000100 0.0
062 P000100 0.0
062 Q000100 0.0
062 R000100 0.5
063 A000100 0
063 B000100 25.6
064 A000100 Y
064 B000100 N
066 A000100 N
067 000100 N
068 A000100 N
068 B000100 N
069 000100 N
070 A010100 Y
070 A020100 Y
070 B010100 N
070 B020100 N
070 C010100 Y
<PAGE> PAGE 8
070 C020100 N
070 D010100 N
070 D020100 N
070 E010100 Y
070 E020100 Y
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 N
070 K010100 Y
070 K020100 N
070 L010100 N
070 L020100 N
070 M010100 N
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 Y
070 R020100 N
071 A000100 1296537
071 B000100 1384267
071 C000100 733111
071 D000100 177
072 A000100 12
072 B000100 51713
072 C000100 0
072 D000100 0
072 E000100 0
072 F000100 3450
072 G000100 96
072 H000100 0
072 I000100 834
072 J000100 223
072 K000100 161
072 L000100 68
072 M000100 69
072 N000100 0
072 O000100 0
072 P000100 0
<PAGE> PAGE 9
072 Q000100 0
072 R000100 37
072 S000100 6
072 T000100 2866
072 U000100 0
072 V000100 0
072 W000100 487
072 X000100 8297
072 Y000100 493
072 Z000100 43909
072AA000100 0
072BB000100 10812
072CC010100 0
072CC020100 23325
072DD010100 36317
072DD020100 6274
072EE000100 0
073 A010100 0.3800
073 A020100 0.3300
073 B000100 0.0000
073 C000100 0.0100
074 A000100 1
074 B000100 3606
074 C000100 0
074 D000100 683828
074 E000100 0
074 F000100 0
074 G000100 0
074 H000100 0
074 I000100 0
074 J000100 357
074 K000100 0
074 L000100 4433
074 M000100 11
074 N000100 692236
074 O000100 890
074 P000100 178
074 Q000100 0
074 R010100 0
074 R020100 0
074 R030100 0
074 R040100 416
074 S000100 0
074 T000100 690752
074 U010100 93418
074 U020100 41717
074 V010100 6.39
074 V020100 6.40
074 W000100 0.0000
074 X000100 47835
074 Y000100 281
<PAGE> PAGE 10
075 A000100 0
075 B000100 765038
076 000100 0.00
013 A000201 ERNST & YOUNG LLP
013 B010201 BOSTON
013 B020201 MA
013 B030201 02116
024 000200 N
028 A010200 3
028 A020200 0
028 A030200 0
028 A040200 0
028 B010200 66
028 B020200 0
028 B030200 0
028 B040200 0
028 C010200 2
028 C020200 0
028 C030200 0
028 C040200 0
028 D010200 118
028 D020200 0
028 D030200 0
028 D040200 1
028 E010200 0
028 E020200 0
028 E030200 0
028 E040200 4
028 F010200 0
028 F020200 0
028 F030200 0
028 F040200 16
028 G010200 189
028 G020200 0
028 G030200 0
028 G040200 21
028 H000200 108
029 000200 N
030 A000200 0
030 B000200 0.00
030 C000200 0.00
031 A000200 0
031 B000200 0
032 000200 0
033 000200 0
034 000200 N
035 000200 0
036 B000200 0
042 A000200 0
042 B000200 0
042 C000200 0
<PAGE> PAGE 11
042 D000200 0
042 E000200 0
042 F000200 0
042 G000200 0
042 H000200 0
043 000200 0
044 000200 0
045 000200 Y
046 000200 N
047 000200 Y
048 000200 0.850
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 N
051 000200 N
052 000200 N
053 A000200 Y
053 B000200 Y
053 C000200 Y
055 A000200 Y
055 B000200 Y
056 000200 Y
057 000200 N
058 A000200 N
059 000200 Y
060 A000200 N
060 B000200 N
061 000200 1000
062 A000200 Y
062 B000200 0.0
<PAGE> PAGE 12
062 C000200 2.3
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 0.0
062 M000200 0.0
062 N000200 0.0
062 O000200 0.0
062 P000200 0.0
062 Q000200 90.9
062 R000200 6.8
063 A000200 0
063 B000200 15.3
064 A000200 N
064 B000200 N
066 A000200 N
067 000200 N
068 A000200 N
068 B000200 Y
069 000200 N
070 A010200 Y
070 A020200 N
070 B010200 N
070 B020200 N
070 C010200 Y
070 C020200 N
070 D010200 Y
070 D020200 N
070 E010200 Y
070 E020200 N
070 F010200 Y
070 F020200 N
070 G010200 Y
070 G020200 N
070 H010200 Y
070 H020200 N
070 I010200 N
070 I020200 N
070 J010200 Y
070 J020200 Y
070 K010200 Y
070 K020200 N
070 L010200 Y
070 L020200 Y
070 M010200 Y
070 M020200 Y
<PAGE> PAGE 13
070 N010200 Y
070 N020200 Y
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 3993
071 B000200 3691
071 C000200 822
071 D000200 449
072 A000200 12
072 B000200 104
072 C000200 0
072 D000200 0
072 E000200 0
072 F000200 8
072 G000200 0
072 H000200 0
072 I000200 1
072 J000200 6
072 K000200 0
072 L000200 0
072 M000200 0
072 N000200 2
072 O000200 0
072 P000200 0
072 Q000200 0
072 R000200 19
072 S000200 4
072 T000200 3
072 U000200 0
072 V000200 0
072 W000200 1
072 X000200 44
072 Y000200 31
072 Z000200 91
072AA000200 0
072BB000200 202
072CC010200 74
072CC020200 0
072DD010200 56
072DD020200 1
072EE000200 0
073 A010200 0.5600
073 A020200 0.5600
073 B000200 0.0000
073 C000200 0.0000
<PAGE> PAGE 14
074 A000200 1
074 B000200 0
074 C000200 25
074 D000200 1003
074 E000200 0
074 F000200 0
074 G000200 0
074 H000200 0
074 I000200 0
074 J000200 91
074 K000200 0
074 L000200 23
074 M000200 0
074 N000200 1143
074 O000200 38
074 P000200 0
074 Q000200 0
074 R010200 0
074 R020200 0
074 R030200 0
074 R040200 1
074 S000200 0
074 T000200 1104
074 U010200 119
074 U020200 10
074 V010200 8.52
074 V020200 8.52
074 W000200 0.0000
074 X000200 13
074 Y000200 0
075 A000200 0
075 B000200 899
076 000200 0.00
013 A000301 ERNST & YOUNG LLP
013 B010301 BOSTON
013 B020301 MA
013 B030301 02116
024 000300 Y
025 A000301 GOLDMAN SACHS
025 B000301 13-5108880
025 C000301 E
025 D000301 3
025 D000302 0
025 D000303 0
025 D000304 0
025 D000305 0
025 D000306 0
025 D000307 0
025 D000308 0
028 A010300 18
028 A020300 0
<PAGE> PAGE 15
028 A030300 0
028 A040300 10
028 B010300 6
028 B020300 0
028 B030300 0
028 B040300 10
028 C010300 39
028 C020300 0
028 C030300 0
028 C040300 157
028 D010300 11
028 D020300 0
028 D030300 0
028 D040300 15
028 E010300 5
028 E020300 0
028 E030300 0
028 E040300 0
028 F010300 105
028 F020300 0
028 F030300 0
028 F040300 0
028 G010300 184
028 G020300 0
028 G030300 0
028 G040300 192
028 H000300 15
029 000300 N
030 A000300 0
030 B000300 0.00
030 C000300 0.00
031 A000300 0
031 B000300 0
032 000300 0
033 000300 0
034 000300 N
035 000300 0
036 B000300 0
042 A000300 0
042 B000300 0
042 C000300 0
042 D000300 0
042 E000300 0
042 F000300 0
042 G000300 0
042 H000300 0
043 000300 0
044 000300 0
045 000300 Y
046 000300 N
047 000300 Y
<PAGE> PAGE 16
048 000300 0.900
048 A010300 0
048 A020300 0.000
048 B010300 0
048 B020300 0.000
048 C010300 0
048 C020300 0.000
048 D010300 0
048 D020300 0.000
048 E010300 0
048 E020300 0.000
048 F010300 0
048 F020300 0.000
048 G010300 0
048 G020300 0.000
048 H010300 0
048 H020300 0.000
048 I010300 0
048 I020300 0.000
048 J010300 0
048 J020300 0.000
048 K010300 0
048 K020300 0.000
049 000300 N
050 000300 N
051 000300 N
052 000300 N
053 A000300 Y
053 B000300 Y
053 C000300 Y
055 A000300 N
055 B000300 N
056 000300 Y
057 000300 N
058 A000300 N
059 000300 Y
060 A000300 Y
060 B000300 Y
061 000300 1000
062 A000300 N
062 B000300 0.0
062 C000300 0.0
062 D000300 0.0
062 E000300 0.0
062 F000300 0.0
062 G000300 0.0
062 H000300 0.0
062 I000300 0.0
062 J000300 0.0
062 K000300 0.0
062 L000300 0.0
<PAGE> PAGE 17
062 M000300 0.0
062 N000300 0.0
062 O000300 0.0
062 P000300 0.0
062 Q000300 0.0
062 R000300 0.0
063 A000300 0
063 B000300 0.0
066 A000300 Y
066 B000300 N
066 C000300 Y
066 D000300 N
066 E000300 N
066 F000300 N
066 G000300 N
067 000300 N
068 A000300 N
068 B000300 N
069 000300 N
070 A010300 Y
070 A020300 N
070 B010300 Y
070 B020300 N
070 C010300 Y
070 C020300 N
070 D010300 Y
070 D020300 N
070 E010300 Y
070 E020300 N
070 F010300 Y
070 F020300 N
070 G010300 Y
070 G020300 N
070 H010300 Y
070 H020300 N
070 I010300 N
070 I020300 N
070 J010300 Y
070 J020300 N
070 K010300 Y
070 K020300 N
070 L010300 Y
070 L020300 Y
070 M010300 Y
070 M020300 Y
070 N010300 Y
070 N020300 N
070 O010300 Y
070 O020300 N
070 P010300 Y
070 P020300 N
<PAGE> PAGE 18
070 Q010300 N
070 Q020300 N
070 R010300 Y
070 R020300 N
071 A000300 1191
071 B000300 1073
071 C000300 847
071 D000300 127
072 A000300 12
072 B000300 2
072 C000300 7
072 D000300 0
072 E000300 0
072 F000300 8
072 G000300 0
072 H000300 0
072 I000300 1
072 J000300 5
072 K000300 0
072 L000300 9
072 M000300 0
072 N000300 2
072 O000300 0
072 P000300 0
072 Q000300 0
072 R000300 13
072 S000300 3
072 T000300 1
072 U000300 0
072 V000300 0
072 W000300 1
072 X000300 43
072 Y000300 31
072 Z000300 -3
072AA000300 94
072BB000300 0
072CC010300 85
072CC020300 0
072DD010300 0
072DD020300 0
072EE000300 55
073 A010300 0.0000
073 A020300 0.0000
073 B000300 0.6000
073 C000300 0.0000
074 A000300 15
074 B000300 0
074 C000300 85
074 D000300 0
074 E000300 0
074 F000300 1045
<PAGE> PAGE 19
074 G000300 0
074 H000300 0
074 I000300 0
074 J000300 0
074 K000300 0
074 L000300 45
074 M000300 0
074 N000300 1190
074 O000300 12
074 P000300 0
074 Q000300 0
074 R010300 0
074 R020300 0
074 R030300 0
074 R040300 0
074 S000300 0
074 T000300 1178
074 U010300 23
074 U020300 80
074 V010300 11.43
074 V020300 11.42
074 W000300 0.0000
074 X000300 45
074 Y000300 0
075 A000300 0
075 B000300 900
076 000300 0.00
013 A000401 ERNST & YOUNG LLP
013 B010401 BOSTON
013 B020401 MA
013 B030401 02116
024 000400 Y
025 A000401 MERRILL LYNCH & CO., INC.
025 B000401 13-5674085
025 C000401 E
025 D000401 7
025 A000402 DELETE
025 D000402 0
025 D000403 0
025 D000404 0
025 D000405 0
025 D000406 0
025 D000407 0
025 D000408 0
028 A010400 9
028 A020400 0
028 A030400 0
028 A040400 0
028 B010400 54
028 B020400 0
028 B030400 0
<PAGE> PAGE 20
028 B040400 3
028 C010400 129
028 C020400 0
028 C030400 0
028 C040400 0
028 D010400 344
028 D020400 0
028 D030400 0
028 D040400 5
028 E010400 383
028 E020400 0
028 E030400 0
028 E040400 77
028 F010400 122
028 F020400 0
028 F030400 0
028 F040400 3
028 G010400 1041
028 G020400 0
028 G030400 0
028 G040400 88
028 H000400 32
029 000400 N
030 A000400 0
030 B000400 0.00
030 C000400 0.00
031 A000400 0
031 B000400 0
032 000400 0
033 000400 0
034 000400 N
035 000400 0
036 B000400 0
042 A000400 0
042 B000400 0
042 C000400 0
042 D000400 0
042 E000400 0
042 F000400 0
042 G000400 0
042 H000400 0
043 000400 0
044 000400 0
045 000400 Y
046 000400 N
047 000400 Y
048 000400 0.750
048 A010400 0
048 A020400 0.000
048 B010400 0
048 B020400 0.000
<PAGE> PAGE 21
048 C010400 0
048 C020400 0.000
048 D010400 0
048 D020400 0.000
048 E010400 0
048 E020400 0.000
048 F010400 0
048 F020400 0.000
048 G010400 0
048 G020400 0.000
048 H010400 0
048 H020400 0.000
048 I010400 0
048 I020400 0.000
048 J010400 0
048 J020400 0.000
048 K010400 0
048 K020400 0.000
049 000400 N
050 000400 N
051 000400 N
052 000400 N
053 A000400 Y
053 B000400 Y
053 C000400 Y
055 A000400 N
055 B000400 N
056 000400 Y
057 000400 N
058 A000400 N
059 000400 Y
060 A000400 Y
060 B000400 Y
061 000400 1000
062 A000400 N
062 B000400 0.0
062 C000400 0.0
062 D000400 0.0
062 E000400 0.0
062 F000400 0.0
062 G000400 0.0
062 H000400 0.0
062 I000400 0.0
062 J000400 0.0
062 K000400 0.0
062 L000400 0.0
062 M000400 0.0
062 N000400 0.0
062 O000400 0.0
062 P000400 0.0
062 Q000400 0.0
<PAGE> PAGE 22
062 R000400 0.0
063 A000400 0
063 B000400 0.0
066 A000400 Y
066 B000400 N
066 C000400 Y
066 D000400 N
066 E000400 N
066 F000400 N
066 G000400 N
067 000400 N
068 A000400 N
068 B000400 N
069 000400 N
070 A010400 Y
070 A020400 N
070 B010400 N
070 B020400 N
070 C010400 Y
070 C020400 N
070 D010400 N
070 D020400 N
070 E010400 Y
070 E020400 N
070 F010400 Y
070 F020400 N
070 G010400 Y
070 G020400 N
070 H010400 Y
070 H020400 N
070 I010400 N
070 I020400 N
070 J010400 Y
070 J020400 Y
070 K010400 Y
070 K020400 N
070 L010400 Y
070 L020400 Y
070 M010400 Y
070 M020400 Y
070 N010400 Y
070 N020400 N
070 O010400 Y
070 O020400 N
070 P010400 Y
070 P020400 N
070 Q010400 N
070 Q020400 N
070 R010400 Y
070 R020400 N
071 A000400 2164
<PAGE> PAGE 23
071 B000400 1333
071 C000400 1017
071 D000400 131
072 A000400 12
072 B000400 2
072 C000400 16
072 D000400 0
072 E000400 0
072 F000400 8
072 G000400 0
072 H000400 0
072 I000400 1
072 J000400 5
072 K000400 0
072 L000400 5
072 M000400 0
072 N000400 2
072 O000400 0
072 P000400 0
072 Q000400 0
072 R000400 13
072 S000400 3
072 T000400 2
072 U000400 0
072 V000400 0
072 W000400 1
072 X000400 40
072 Y000400 27
072 Z000400 5
072AA000400 208
072BB000400 0
072CC010400 127
072CC020400 0
072DD010400 2
072DD020400 1
072EE000400 36
073 A010400 0.0400
073 A020400 0.0400
073 B000400 0.5000
073 C000400 0.0000
074 A000400 3
074 B000400 0
074 C000400 85
074 D000400 13
074 E000400 8
074 F000400 1895
074 G000400 0
074 H000400 0
074 I000400 0
074 J000400 20
074 K000400 0
<PAGE> PAGE 24
074 L000400 27
074 M000400 0
074 N000400 2051
074 O000400 15
074 P000400 0
074 Q000400 0
074 R010400 0
074 R020400 0
074 R030400 0
074 R040400 1
074 S000400 0
074 T000400 2035
074 U010400 57
074 U020400 86
074 V010400 14.25
074 V020400 14.23
074 W000400 0.0000
074 X000400 38
074 Y000400 0
075 A000400 0
075 B000400 1051
076 000400 0.00
SIGNATURE JAMES O. YOST
TITLE ASSISTANT TREASURER
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 031
<NAME> MFS SMALL CAP VALUE FUND - CLASS A
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 1101686
<INVESTMENTS-AT-VALUE> 1129573
<RECEIVABLES> 45528
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 15093
<TOTAL-ASSETS> 1190194
<PAYABLE-FOR-SECURITIES> 12485
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 81
<TOTAL-LIABILITIES> 12566
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1058969
<SHARES-COMMON-STOCK> 23445
<SHARES-COMMON-PRIOR> 41760
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 90777
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 27882
<NET-ASSETS> 1177628
<DIVIDEND-INCOME> 6511
<INTEREST-INCOME> 2531
<OTHER-INCOME> (74)
<EXPENSES-NET> (11729)
<NET-INVESTMENT-INCOME> (2761)
<REALIZED-GAINS-CURRENT> 93824
<APPREC-INCREASE-CURRENT> 85364
<NET-CHANGE-FROM-OPS> 176427
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (110)
<DISTRIBUTIONS-OF-GAINS> (21973)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 3652
<NUMBER-OF-SHARES-REDEEMED> (24428)
<SHARES-REINVESTED> 2461
<NET-CHANGE-IN-ASSETS> 273565
<ACCUMULATED-NII-PRIOR> 277
<ACCUMULATED-GAINS-PRIOR> 55038
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 8120
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 43292
<AVERAGE-NET-ASSETS> 899755
<PER-SHARE-NAV-BEGIN> 10.02
<PER-SHARE-NII> (0.03)
<PER-SHARE-GAIN-APPREC> 2.04
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> (0.60)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 11.43
<EXPENSE-RATIO> 1.34
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 032
<NAME> MFS SMALL CAP VALUE FUND - CLASS I
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 1101686
<INVESTMENTS-AT-VALUE> 1129573
<RECEIVABLES> 45528
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 15093
<TOTAL-ASSETS> 1190194
<PAYABLE-FOR-SECURITIES> 12485
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 81
<TOTAL-LIABILITIES> 12566
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1058969
<SHARES-COMMON-STOCK> 79620
<SHARES-COMMON-PRIOR> 48489
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 90777
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 27882
<NET-ASSETS> 1177628
<DIVIDEND-INCOME> 6511
<INTEREST-INCOME> 2531
<OTHER-INCOME> (74)
<EXPENSES-NET> (11729)
<NET-INVESTMENT-INCOME> (2761)
<REALIZED-GAINS-CURRENT> 93824
<APPREC-INCREASE-CURRENT> 85364
<NET-CHANGE-FROM-OPS> 176427
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (167)
<DISTRIBUTIONS-OF-GAINS> (33239)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 34369
<NUMBER-OF-SHARES-REDEEMED> (6966)
<SHARES-REINVESTED> 3728
<NET-CHANGE-IN-ASSETS> 273565
<ACCUMULATED-NII-PRIOR> 277
<ACCUMULATED-GAINS-PRIOR> 55038
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 8120
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 43292
<AVERAGE-NET-ASSETS> 899755
<PER-SHARE-NAV-BEGIN> 10.02
<PER-SHARE-NII> (0.03)
<PER-SHARE-GAIN-APPREC> 2.03
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> (0.60)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 11.42
<EXPENSE-RATIO> 1.34
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 041
<NAME> MFS STRATEGIC VALUE FUND CLASS A
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 1874155
<INVESTMENTS-AT-VALUE> 2001029
<RECEIVABLES> 46594
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 3091
<TOTAL-ASSETS> 2050714
<PAYABLE-FOR-SECURITIES> 14507
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 888
<TOTAL-LIABILITIES> 15395
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1695646
<SHARES-COMMON-STOCK> 56745
<SHARES-COMMON-PRIOR> 54888
<ACCUMULATED-NII-CURRENT> 4646
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 208165
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 126862
<NET-ASSETS> 2035319
<DIVIDEND-INCOME> 15996
<INTEREST-INCOME> 2277
<OTHER-INCOME> (179)
<EXPENSES-NET> (13172)
<NET-INVESTMENT-INCOME> 4922
<REALIZED-GAINS-CURRENT> 208299
<APPREC-INCREASE-CURRENT> 127058
<NET-CHANGE-FROM-OPS> 340279
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (2574)
<DISTRIBUTIONS-OF-GAINS> (28888)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 5430
<NUMBER-OF-SHARES-REDEEMED> (6555)
<SHARES-REINVESTED> 2982
<NET-CHANGE-IN-ASSETS> 1284431
<ACCUMULATED-NII-PRIOR> 3050
<ACCUMULATED-GAINS-PRIOR> 35588
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 7902
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 40135
<AVERAGE-NET-ASSETS> 1050927
<PER-SHARE-NAV-BEGIN> 10.66
<PER-SHARE-NII> 0.05
<PER-SHARE-GAIN-APPREC> 4.08
<PER-SHARE-DIVIDEND> (0.04)
<PER-SHARE-DISTRIBUTIONS> (0.50)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 14.25
<EXPENSE-RATIO> 1.27
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 042
<NAME> MFS STRATEGIC VALUE FUND CLASS I
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 1874155
<INVESTMENTS-AT-VALUE> 2001029
<RECEIVABLES> 46594
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 3091
<TOTAL-ASSETS> 2050714
<PAYABLE-FOR-SECURITIES> 14507
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 888
<TOTAL-LIABILITIES> 15395
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1695646
<SHARES-COMMON-STOCK> 86177
<SHARES-COMMON-PRIOR> 15547
<ACCUMULATED-NII-CURRENT> 4646
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 208165
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 126862
<NET-ASSETS> 2035319
<DIVIDEND-INCOME> 15996
<INTEREST-INCOME> 2277
<OTHER-INCOME> (179)
<EXPENSES-NET> (13172)
<NET-INVESTMENT-INCOME> 4922
<REALIZED-GAINS-CURRENT> 208299
<APPREC-INCREASE-CURRENT> 127058
<NET-CHANGE-FROM-OPS> 340279
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (615)
<DISTRIBUTIONS-OF-GAINS> (6903)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 75461
<NUMBER-OF-SHARES-REDEEMED> (5544)
<SHARES-REINVESTED> 713
<NET-CHANGE-IN-ASSETS> 1284431
<ACCUMULATED-NII-PRIOR> 3050
<ACCUMULATED-GAINS-PRIOR> 35588
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 7902
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 40135
<AVERAGE-NET-ASSETS> 1050927
<PER-SHARE-NAV-BEGIN> 10.65
<PER-SHARE-NII> 0.05
<PER-SHARE-GAIN-APPREC> 4.07
<PER-SHARE-DIVIDEND> (0.04)
<PER-SHARE-DISTRIBUTIONS> (0.50)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 14.23
<EXPENSE-RATIO> 1.27
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 021
<NAME> EMERGING MARKETS DEBT FUND CLASS A
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 1018955
<INVESTMENTS-AT-VALUE> 1028501
<RECEIVABLES> 113786
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 944
<TOTAL-ASSETS> 1143231
<PAYABLE-FOR-SECURITIES> 38303
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 858
<TOTAL-LIABILITIES> 39161
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1240366
<SHARES-COMMON-STOCK> 119430
<SHARES-COMMON-PRIOR> 100021
<ACCUMULATED-NII-CURRENT> 60670
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (206669)
<ACCUM-APPREC-OR-DEPREC> 9703
<NET-ASSETS> 1104070
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 104021
<OTHER-INCOME> 0
<EXPENSES-NET> (13307)
<NET-INVESTMENT-INCOME> 90714
<REALIZED-GAINS-CURRENT> (202493)
<APPREC-INCREASE-CURRENT> 74356
<NET-CHANGE-FROM-OPS> (37423)
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (56343)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 12476
<NUMBER-OF-SHARES-REDEEMED> (599)
<SHARES-REINVESTED> 7532
<NET-CHANGE-IN-ASSETS> 144325
<ACCUMULATED-NII-PRIOR> 26483
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> (3546)
<GROSS-ADVISORY-FEES> 7617
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 43708
<AVERAGE-NET-ASSETS> 898792
<PER-SHARE-NAV-BEGIN> 9.58
<PER-SHARE-NII> 0.81
<PER-SHARE-GAIN-APPREC> (1.31)
<PER-SHARE-DIVIDEND> (0.56)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 8.52
<EXPENSE-RATIO> 1.56
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 022
<NAME> EMERGING MARKETS DEBT FUND CLASS I
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 1018955
<INVESTMENTS-AT-VALUE> 1028501
<RECEIVABLES> 113786
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 944
<TOTAL-ASSETS> 1143231
<PAYABLE-FOR-SECURITIES> 38303
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 858
<TOTAL-LIABILITIES> 39161
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1240366
<SHARES-COMMON-STOCK> 10097
<SHARES-COMMON-PRIOR> 126
<ACCUMULATED-NII-CURRENT> 60670
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (206669)
<ACCUM-APPREC-OR-DEPREC> 9703
<NET-ASSETS> 1104070
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 104021
<OTHER-INCOME> 0
<EXPENSES-NET> (13307)
<NET-INVESTMENT-INCOME> 90714
<REALIZED-GAINS-CURRENT> (202493)
<APPREC-INCREASE-CURRENT> 74356
<NET-CHANGE-FROM-OPS> (37423)
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (814)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 11715
<NUMBER-OF-SHARES-REDEEMED> (1852)
<SHARES-REINVESTED> 108
<NET-CHANGE-IN-ASSETS> 144325
<ACCUMULATED-NII-PRIOR> 26483
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> (3546)
<GROSS-ADVISORY-FEES> 7617
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 43708
<AVERAGE-NET-ASSETS> 898792
<PER-SHARE-NAV-BEGIN> 9.58
<PER-SHARE-NII> 0.78
<PER-SHARE-GAIN-APPREC> (1.28)
<PER-SHARE-DIVIDEND> (0.56)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 8.52
<EXPENSE-RATIO> 1.56
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 011
<NAME> MFS GOVERNMENT MORTGAGE FUND CLASS A
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 709379243
<INVESTMENTS-AT-VALUE> 687433801
<RECEIVABLES> 4790617
<ASSETS-OTHER> 11081
<OTHER-ITEMS-ASSETS> 464
<TOTAL-ASSETS> 692235963
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 1484422
<TOTAL-LIABILITIES> 1484422
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 764622381
<SHARES-COMMON-STOCK> 93417540
<SHARES-COMMON-PRIOR> 98097509
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> (156543)
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (51704132)
<ACCUM-APPREC-OR-DEPREC> (22010165)
<NET-ASSETS> 690751541
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 51712818
<OTHER-INCOME> 0
<EXPENSES-NET> (7803654)
<NET-INVESTMENT-INCOME> 43909164
<REALIZED-GAINS-CURRENT> (10812341)
<APPREC-INCREASE-CURRENT> (23325499)
<NET-CHANGE-FROM-OPS> 9771324
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (36316688)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> (1390020)
<NUMBER-OF-SHARES-SOLD> 31993681
<NUMBER-OF-SHARES-REDEEMED> (39521723)
<SHARES-REINVESTED> 2848073
<NET-CHANGE-IN-ASSETS> (121357946)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> (184277)
<OVERDIST-NET-GAINS-PRIOR> (42192909)
<GROSS-ADVISORY-FEES> 3450182
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 8297030
<AVERAGE-NET-ASSETS> 765037528
<PER-SHARE-NAV-BEGIN> 6.69
<PER-SHARE-NII> 0.39
<PER-SHARE-GAIN-APPREC> (0.30)
<PER-SHARE-DIVIDEND> (0.38)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> (0.01)
<PER-SHARE-NAV-END> 6.39
<EXPENSE-RATIO> 0.93
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 012
<NAME> MFS GOVERNMENT MORTGAGE FUND CLASS B
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 709379243
<INVESTMENTS-AT-VALUE> 687433801
<RECEIVABLES> 4790617
<ASSETS-OTHER> 11081
<OTHER-ITEMS-ASSETS> 464
<TOTAL-ASSETS> 692235963
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 1484422
<TOTAL-LIABILITIES> 1484422
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 764622381
<SHARES-COMMON-STOCK> 14717232
<SHARES-COMMON-PRIOR> 23190632
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> (156543)
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (51704132)
<ACCUM-APPREC-OR-DEPREC> (22010165)
<NET-ASSETS> 690751541
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 51712818
<OTHER-INCOME> 0
<EXPENSES-NET> (7803654)
<NET-INVESTMENT-INCOME> 43909164
<REALIZED-GAINS-CURRENT> (10812341)
<APPREC-INCREASE-CURRENT> (23325499)
<NET-CHANGE-FROM-OPS> 9771324
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (6273606)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> (240095)
<NUMBER-OF-SHARES-SOLD> 2049005
<NUMBER-OF-SHARES-REDEEMED> (11091050)
<SHARES-REINVESTED> 568645
<NET-CHANGE-IN-ASSETS> (121357946)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> (184277)
<OVERDIST-NET-GAINS-PRIOR> (42192909)
<GROSS-ADVISORY-FEES> 3450182
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 8297030
<AVERAGE-NET-ASSETS> 765037528
<PER-SHARE-NAV-BEGIN> 6.70
<PER-SHARE-NII> 0.34
<PER-SHARE-GAIN-APPREC> (0.30)
<PER-SHARE-DIVIDEND> (0.33)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> (0.01)
<PER-SHARE-NAV-END> 6.40
<EXPENSE-RATIO> 1.68
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000783740
<NAME> MFS SERIES TRUST X
<SERIES>
<NUMBER> 013
<NAME> MFS GOVERNMENT MORTGAGE FUND CLASS I
<MULTIPLIER> 1
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> JUL-31-1999
<PERIOD-START> AUG-01-1998
<PERIOD-END> JUL-31-1999
<INVESTMENTS-AT-COST> 709379243
<INVESTMENTS-AT-VALUE> 687433801
<RECEIVABLES> 4790617
<ASSETS-OTHER> 11081
<OTHER-ITEMS-ASSETS> 464
<TOTAL-ASSETS> 692235963
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 1484422
<TOTAL-LIABILITIES> 1484422
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 764622381
<SHARES-COMMON-STOCK> 9571
<SHARES-COMMON-PRIOR> 7649
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> (156543)
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> (51704132)
<ACCUM-APPREC-OR-DEPREC> (22010165)
<NET-ASSETS> 690751541
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 51712818
<OTHER-INCOME> 0
<EXPENSES-NET> (7803654)
<NET-INVESTMENT-INCOME> 43909164
<REALIZED-GAINS-CURRENT> (10812341)
<APPREC-INCREASE-CURRENT> (23325499)
<NET-CHANGE-FROM-OPS> 9771324
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (3294)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> (126)
<NUMBER-OF-SHARES-SOLD> 2401
<NUMBER-OF-SHARES-REDEEMED> (997)
<SHARES-REINVESTED> 518
<NET-CHANGE-IN-ASSETS> (121357946)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> (184277)
<OVERDIST-NET-GAINS-PRIOR> (42192909)
<GROSS-ADVISORY-FEES> 3450182
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 8297030
<AVERAGE-NET-ASSETS> 765037528
<PER-SHARE-NAV-BEGIN> 6.69
<PER-SHARE-NII> 0.41
<PER-SHARE-GAIN-APPREC> (0.30)
<PER-SHARE-DIVIDEND> (0.41)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> (0.01)
<PER-SHARE-NAV-END> 6.38
<EXPENSE-RATIO> 0.68
</TABLE>
Report of Independent Auditors
To the Trustees
MFS Series Trust X
In planning and performing our audits of the financial statements of MFS
Emerging Markets Debt Fund, MFS Small Cap Value Fund, and MFS Strategic Value
Fund ("the funds") three of the funds comprising the MFS Series Trust X, for the
year ended July 31, 1999, we considered its internal control, including control
activities for safeguarding securities, in order to determine our auditing
procedures for the purpose of expressing our opinion on the financial statements
and to comply with the requirements of Form N-SAR, and not to provide assurance
on the internal control.
The management of the Funds is responsible for establishing and maintaining
internal control. In fulfilling this responsibility, estimates and judgments by
management are required to assess the expected benefits and related costs of
controls. Generally, controls that are relevant to an audit pertain to the
entity's objective of preparing financial statements for external purposes that
are fairly presented in conformity with generally accepted accounting
principles. Those controls include the safeguarding of assets against
unauthorized acquisition, use or disposition.
Because of inherent limitations in internal control, errors or fraud may occur
and not be detected. Also, projection of any evaluation of internal control to
future periods is subject to the risk that it may become inadequate because of
changes in conditions or that the effectiveness of the design and operation may
deteriorate.
Our consideration of internal control would not necessarily disclose all matters
in internal control that might be material weaknesses under standards
established by the American Institute of Certified Public Accountants. A
material weakness is a condition in which the design or operation of one or more
of the specific internal control components does not reduce to a relatively low
level the risk that errors or fraud in amounts that would be material in
relation to the financial statements being audited may occur and not be detected
within a timely period by employees in the normal course of performing their
assigned functions. However, we noted no matters involving internal control and
its operation, including controls for safeguarding securities, that we consider
to be material weaknesses as defined above at July 31, 1999.
This report is intended solely for the information and use of the trustees and
management of MFS Series Trust X and the Securities and Exchange Commission and
is not intended to be and should not be used by anyone other than these
specified parties.
ERNST & YOUNG LLP
September 9, 1999
SUB-ITEM 77-H
MFS SERIES TRUST X ON BEHALF OF:
MFS STRATEGIC VALUE FUND (" SVF")
MFS SMALL CAP VALUE FUND ("SCV")
MFS EMERGING MARKETS DEBT FUND ("EMF")
As of July 31, 1999, the following entities beneficially owning more
than 25% of any one Series' voting securities, thereby becoming controlling
entities of such Series, are those entities listed as follows:
<TABLE>
<CAPTION>
SHARES
SERIES OWNER AND ADDRESS OWNED
- ------ ----------------- -----
<S> <C> <C>
MFS Strategic Value Fund
Class A Shares MFS Fund Distributors, Inc. 86.18%
c/o Massachusetts Financial Services Company
Attn: Thomas B. Hastings
500 Boylston Street - 15th Floor
Boston, MA 02116-3740
Class I Shares TRS MFS Defined Contribuiton Plan 99.98%
C/O Mark Leary
Massachusetts Financial Services Company
500 Boylston Street
Boston, MA 02116-3740
MFS Small Cap Value Fund
Class I Shares TRS MFS Defined Contribution Plan 99.98%
c/o Mark Leary
Massachusetts Financial Services
500 Boylston Street
Boston, Massachusetts 02116-3740
MFS Emerging Markets Debt Fund MFS Fund Distributors Inc. 90.01%
Class A Shares c/o Massachusetts Financial Services Co.
Attn: Thomas B. Hastings
500 Boylston Street - 15th Floor
Boston, MA 02116-3740
Class I Shares MFS Defined Contribution Plan 99.83%
c/o Mark Leary
Massachusetts Financial Services Company
500 Boylston Street
Boston, Massachusetts 02116-3740
As of July 31, 1999, entities no longer beneficially owning more than
25% of any one Series' voting securities, thereby ceasing to be controlling
entities of such Series, are as follows:
SERIES OWNER AND ADDRESS
- ------ -----------------
MFS Small Cap Value Fund
Class A Shares MFS Fund Distributors Inc.
C/o Massachusetts Financial Services Company
Attn: Thomas B. Hastings
500 Boylston Street-15th Floor
Boston, MA 02116-3740
</TABLE>
INDEPENDENT AUDITORS' REPORT
To the Trustees and Shareholders of MFS Government Mortgage Fund:
In planning and performing our audit of the financial statements of MFS
Government Mortgage Fund (a series of MFS Series Trust X) (the "Fund") for the
year ended July 31, 1999 (on which we have issued our report dated September 9,
1999), we considered its internal control, including control activities for
safeguarding securities, in order to determine our auditing procedures for the
purpose of expressing our opinion on the financial statements and to comply with
the requirements of Form N-SAR, and not to provide assurance on the Fund's
internal control.
The management of the Fund is responsible for establishing and maintaining
internal control. In fulfilling this responsibility, estimates and judgments by
management are required to assess the expected benefits and related costs of
controls. Generally, controls that are relevant to an audit pertain to the
entity's objective of preparing financial statements for external purposes that
are fairly presented in conformity with generally accepted accounting
principles. Those controls include the safeguarding of assets against
unauthorized acquisition, use or disposition.
Because of inherent limitations in any internal control, misstatements due to
error or fraud may occur and not be detected. Also, projections of any
evaluation of internal control to future periods are subject to the risk that
the internal control may become inadequate because of changes in conditions or
that the degree of compliance with policies or procedures deteriorates.
Our consideration of the Fund's internal control would not necessarily disclose
all matters in internal control that might be material weaknesses under
standards established by the American Institute of Certified Public Accountants.
A material weakness is a condition in which the design or operation of one or
more of the internal control components does not reduce to a relatively low
level the risk that misstatements caused by error or fraud in amounts that would
be material in relation to the financial statements being audited may occur and
not be detected within a timely period by employees in the normal course of
performing their assigned functions. However, we noted no matters involving the
Fund's internal control and its operation, including controls for safeguarding
securities, that we consider to be material weaknesses as defined above as of
July 31, 1999.
This report is intended solely for the information and use of management, the
Board of Trustees of the Series, and the Securities and Exchange Commission and
is not intended to be and should not be used by anyone other than these
specified parties.
Deloitte & Touche LLP
Boston, MA
September 9, 1999
