EFIR EGPI Firecreek Inc (CE)

000 A000000 01/31/2013
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 111 HUNTINGTON AVENUE
002 B000000 BOSTON
002 C000000 MA
002 D010000 02199
003  000000 N
004  000000 N
005  000000 N
006  000000 N
007 A000000 Y
007 B000000 12
007 C011800 18
007 C021800 MFS Emerging Markets Debt Fund
007 C031800 N
007 C012100 21
007 C022100 MFS Emerging Markets Debt Local Currency Fund
007 C032100 N
008 A00AA01 MASSACHUSETTS FINANCIAL SERVICES COMPANY
008 B00AA01 A
008 C00AA01 801-17352
008 D01AA01 BOSTON
008 D02AA01 MA
008 D03AA01 02199
010 A00AA01 MASSACHUSETTS FINANCIAL SERVICES
010 B00AA01 801-17352
010 C01AA01 BOSTON
010 C02AA01 MA
010 C03AA01 02199
011 A00AA01 MFS FUND DISTRIBUTORS, INC.
011 B00AA01 8-27864
011 C01AA01 BOSTON
011 C02AA01 MA
011 C03AA01 02199
012 A00AA01 MFS SERVICE CENTER, INC.
012 B00AA01 84-1316
012 C01AA01 BOSTON
012 C02AA01 MA
012 C03AA01 02199
013 A001801 ERNST & YOUNG LLP
013 B011801 BOSTON

013 B021801 MA
013 B031801 02116
013 A002101 ERNST & YOUNG LLP
013 B012101 BOSTON
013 B022101 MA
013 B032101 02116
015 A001801 STATE STREET BANK AND TRUST COMPANY
015 B001801 C
015 C011801 BOSTON
015 C021801 MA
015 C031801 02110
015 E011801 X
015 A001802 STATE STREET BANK INTERNATIONAL
015 B001802 S
015 C011802 BOSTON
015 C021802 MA
015 C031802 02110
015 E041802 X
015 A001803 THE BANK OF NEW YORK
015 B001803 S
015 C011803 NEW YORK
015 C021803 NY
015 C031803 10286
015 E011803 X
015 A001804 BANK OF AMERICA/MERRILL LYNCH
015 B001804 C
015 C011804 Charlotte
015 C021804 NC
015 C031804 28255
015 E011804 X
015 A001805 GOLDMAN, SACHS & CO.
015 B001805 C
015 C011805 NEW YORK
015 C021805 NY
015 C031805 10004
015 E011805 X
015 A002101 STATE STREET BANK AND TRUST COMPANY
015 B002101 C
015 C012101 BOSTON
015 C022101 MA
015 C032101 02110
015 E012101 X
015 A002102 BANK OF AMERICA/MERRILL LYNCH
015 B002102 C
015 C012102 Charlotte
015 C022102 NC
015 C032102 28255
015 E012102 X
015 A002103 STATE STREET BANK INTERNATIONAL
015 B002103 S
015 C012103 BOSTON

015 C022103 MA
015 C032103 02116
015 E042103 X
015 A002104 THE BANK OF NEW YORK
015 B002104 S
015 C012104 NEW YORK
015 C022104 NY
015 C032104 10286
015 E012104 X
015 A002105 GOLDMAN, SACHS & CO.
015 B002105 C
015 C012105 NEW YORK
015 C022105 NY
015 C032105 10004
015 E012105 X
018  00AA00 Y
019 A00AA00 Y
019 B00AA00   82
019 C00AA00 MASSFINSER
020 A000001 BANK OF AMERICA/MERRILL LYNCH
020 B000001 00-0000000
020 C000001     18
021  000000       18
022 A000001 JPMORGAN CHASE & CO.
022 B000001 13-3224017
022 C000001    462168
022 D000001    191944
022 A000002 BANK OF NEW YORK CO., INC.
022 B000002 13-3878175
022 C000002    347162
022 D000002    141215
022 A000003 CITIGROUP, INC.
022 B000003 13-3187336
022 C000003    314779
022 D000003    139555
022 A000004 BANK OF AMERICA/MERRILL LYNCH
022 B000004 00-0000000
022 C000004    165091
022 D000004    221451
022 A000005 BARCLAYS PLC
022 B000005 00-0000000
022 C000005    201143
022 D000005    148486
022 A000006 MORGAN STANLEY
022 B000006 13-2655998
022 C000006    125879
022 D000006    157088
022 A000007 GOLDMAN SACHS GROUP, INC.
022 B000007 13-5108880
022 C000007    123781
022 D000007     70946

022 A000008 CREDIT SUISSE GROUP
022 B000008 13-5659485
022 C000008     88655
022 D000008     67260
022 A000009 NOMURA HOLDINGS, INC.
022 B000009 00-0000000
022 C000009    103332
022 D000009     52530
022 A000010 BNP Paribas
022 B000010 00-0000000
022 C000010    108919
022 D000010     21978
023 C000000    3700512
023 D000000    2391493
024  001800 N
024  002100 Y
025 D001801       0
025 A002101 CREDIT SUISSE GROUP
025 B002101 13-5659485
025 C002101 D
025 D002101    2161
026 A000000 N
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
028 A011800    315738
028 A021800     18034
028 A031800         0
028 A041800    124717
028 B011800    366232
028 B021800     19104
028 B031800         0
028 B041800     91115
028 C011800    260113
028 C021800     19868
028 C031800         0
028 C041800    136091
028 D011800    282211
028 D021800     20207
028 D031800         0
028 D041800    128180
028 E011800    281270
028 E021800     62672
028 E031800         0
028 E041800    153108

028 F011800    416832
028 F021800     21719
028 F031800         0
028 F041800    139021
028 G011800   1922396
028 G021800    161604
028 G031800         0
028 G041800    772232
028 H001800    460208
028 A012100      6025
028 A022100        81
028 A032100         0
028 A042100        64
028 B012100      2348
028 B022100        88
028 B032100         0
028 B042100         8
028 C012100       760
028 C022100        83
028 C032100         0
028 C042100        25
028 D012100      2778
028 D022100        83
028 D032100         0
028 D042100        57
028 E012100      2684
028 E022100        82
028 E032100         0
028 E042100        82
028 F012100      4363
028 F022100        84
028 F032100         0
028 F042100       179
028 G012100     18958
028 G022100       501
028 G032100         0
028 G042100       415
028 H002100      6510
029  001800 Y
029  002100 Y
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030 B001800  4.75
030 C001800  0.00
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030 B002100  4.75
030 C002100  0.00
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031 A002100      6
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032  001800   1578

032  002100     24
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034  001800 Y
034  002100 Y
035  001800     79
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036 A001800 N
036 B001800      0
036 A002100 N
036 B002100      0
037  001800 N
037  002100 N
038  001800      0
038  002100      0
039  001800 N
039  002100 N
040  001800 Y
040  002100 Y
041  001800 Y
041  002100 Y
042 A001800   0
042 B001800   0
042 C001800 100
042 D001800   0
042 E001800   0
042 F001800   0
042 G001800   0
042 H001800   0
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042 B002100   0
042 C002100 100
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042 F002100   0
042 G002100   0
042 H002100   0
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043  002100     13
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045  002100 Y
046  001800 N
046  002100 N
047  001800 Y
047  002100 Y
048  001800  0.000
048 A011800  1000000
048 A021800 0.750
048 B011800        0

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048 C011800        0
048 C021800 0.000
048 D011800        0
048 D021800 0.000
048 E011800        0
048 E021800 0.000
048 F011800        0
048 F021800 0.000
048 G011800        0
048 G021800 0.000
048 H011800        0
048 H021800 0.000
048 I011800        0
048 I021800 0.000
048 J011800        0
048 J021800 0.000
048 K011800  1000000
048 K021800 0.700
048  002100  0.000
048 A012100  1000000
048 A022100 0.750
048 B012100        0
048 B022100 0.000
048 C012100        0
048 C022100 0.000
048 D012100        0
048 D022100 0.000
048 E012100        0
048 E022100 0.000
048 F012100        0
048 F022100 0.000
048 G012100        0
048 G022100 0.000
048 H012100        0
048 H022100 0.000
048 I012100        0
048 I022100 0.000
048 J012100        0
048 J022100 0.000
048 K012100  1000000
048 K022100 0.700
049  001800 N
049  002100 N
050  001800 N
050  002100 N
051  001800 N
051  002100 N
052  001800 N
052  002100 N
053 A001800 Y

053 B001800 Y
053 C001800 N
053 A002100 Y
053 B002100 Y
053 C002100 N
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
055 A001800 N
055 B001800 N
055 A002100 N
055 B002100 N
056  001800 Y
056  002100 Y
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057  002100 N
058 A001800 N
058 A002100 N
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060 A001800 N
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060 A002100 N
060 B002100 N
061  001800     1000
061  002100     1000
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062 C001800   0.0
062 D001800   0.0
062 E001800   0.0
062 F001800   0.0
062 G001800   0.0
062 H001800   0.0
062 I001800   0.0
062 J001800   0.0
062 K001800   0.1
062 L001800   0.0
062 M001800   1.0

062 N001800   0.0
062 O001800   0.0
062 P001800   0.0
062 Q001800  89.7
062 R001800   9.0
062 A002100 Y
062 B002100   0.0
062 C002100   0.0
062 D002100   0.0
062 E002100   0.0
062 F002100   0.0
062 G002100   0.0
062 H002100   0.0
062 I002100   0.0
062 J002100   0.0
062 K002100   0.0
062 L002100   0.0
062 M002100   0.0
062 N002100   0.0
062 O002100   0.0
062 P002100   0.0
062 Q002100  92.9
062 R002100   3.5
063 A001800   0
063 B001800 11.5
063 A002100   0
063 B002100  9.1
064 A001800 N
064 B001800 N
064 A002100 N
064 B002100 N
066 A001800 N
066 A002100 N
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067  002100 N
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068 A002100 N
068 B002100 Y
069  001800 N
069  002100 N
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070 B011800 Y
070 B021800 N
070 C011800 Y
070 C021800 Y
070 D011800 Y
070 D021800 N
070 E011800 Y
070 E021800 Y

070 F011800 Y
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070 G011800 Y
070 G021800 Y
070 H011800 Y
070 H021800 N
070 I011800 Y
070 I021800 N
070 J011800 Y
070 J021800 Y
070 K011800 Y
070 K021800 Y
070 L011800 Y
070 L021800 Y
070 M011800 Y
070 M021800 Y
070 N011800 Y
070 N021800 N
070 O011800 Y
070 O021800 N
070 P011800 Y
070 P021800 Y
070 Q011800 N
070 Q021800 N
070 R011800 Y
070 R021800 N
070 A012100 Y
070 A022100 N
070 B012100 Y
070 B022100 N
070 C012100 Y
070 C022100 Y
070 D012100 Y
070 D022100 N
070 E012100 Y
070 E022100 Y
070 F012100 Y
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070 G012100 Y
070 G022100 Y
070 H012100 Y
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070 I012100 Y
070 I022100 N
070 J012100 Y
070 J022100 Y
070 K012100 Y
070 K022100 Y
070 L012100 Y
070 L022100 Y
070 M012100 Y

070 M022100 Y
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070 O022100 N
070 P012100 Y
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070 R012100 Y
070 R022100 N
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071 B001800   1449531
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071 D001800   25
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071 B002100     10156
071 C002100     29124
071 D002100   35
072 A001800  6
072 B001800   167857
072 C001800      352
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072 F001800    22120
072 G001800      274
072 H001800        0
072 I001800     2588
072 J001800      250
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072 M001800       31
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072 T001800     4982
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072 Y001800      946
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072AA001800   124364
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072CC011800   103472
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072DD011800    33924
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072 C002100       -4
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077 A000000 Y
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077 I000000 Y
077 J000000 N
077 K000000 N
077 L000000 N
077 M000000 N
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077 P000000 N
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SIGNATURE   KINO CLARK
TITLE       ASSISTANT TREASURER