<PAGE> PAGE 1
000 B000000 12/31/1998
000 C000000 0000730044
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 6.1
000 J000000 A
001 A000000 MSDW U.S. GOVERNMENT SECURITIES TRUST
001 B000000 811-3870
001 C000000 2123922550
002 A000000 TWO WORLD TRADE CENTER
002 B000000 NEW YORK
002 C000000 NY
002 D010000 10048
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 N
007 B000000 0
007 C010100 1
007 C010200 2
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 A000001 MORGAN STANLEY DEAN WITTER ADVISORS INC.
008 B000001 A
008 C000001 801-42061
008 D010001 NEW YORK
008 D020001 NY
008 D030001 10048
011 A000001 MORGAN STANLEY DEAN WITTER DISTRIBUTORS INC.
011 B000001 8-11745
011 C010001 NEW YORK
011 C020001 NY
011 C030001 10048
012 A000001 MORGAN STANLEY DEAN WITTER TRUST FSB
012 B000001 84-1785
012 C010001 JERSEY CITY
012 C020001 NJ
012 C030001 07311
013 A000001 PRICEWATERHOUSECOOPERS LLP
013 B010001 NEW YORK
013 B020001 NY
<PAGE> PAGE 2
013 B030001 10036
014 A000001 DEAN WITTER REYNOLDS INC.
014 B000001 8-14172
014 A000002 MORGAN STANLEY & CO. INCORPORATED
014 B000002 8-15869
015 A000001 THE BANK OF NEW YORK
015 B000001 C
015 C010001 NEW YORK
015 C020001 NY
015 C030001 10286
015 E010001 X
018 000000 Y
019 A000000 Y
019 B000000 119
019 C000000 MSDW-FUNDS
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 WARBURG DILLION READ LLC
022 B000001 13-3873456
022 C000001 476184
022 D000001 370807
022 A000002 GOLDMAN SACHS & CO.
022 B000002 13-5108880
022 C000002 544724
022 D000002 256161
022 A000003 BARCLAYS CAPITAL GROUP
022 B000003 13-3551367
022 C000003 399764
022 D000003 308280
022 A000004 FUJI SECURITIES INC.
022 B000004 36-2880742
022 C000004 214765
022 D000004 430252
022 A000005 LEHMAN BROTHERS INC.
022 B000005 13-2518466
022 C000005 257512
022 D000005 166207
022 A000006 PRUDENTIAL SECURITIES INC.
022 B000006 22-2347336
022 C000006 134243
022 D000006 172887
022 A000007 PAINEWEBBER INC.
<PAGE> PAGE 3
022 B000007 13-2638166
022 C000007 125025
022 D000007 59924
022 A000008 NATIONSBANC CAPITAL CORP.
022 B000008 56-1684171
022 C000008 68514
022 D000008 114705
022 A000009 CS FIRST BOSTON CORP.
022 B000009 13-5659485
022 C000009 97506
022 D000009 60463
022 A000010 SALOMON BROTHERS INC.
022 B000010 13-3082694
022 C000010 79095
022 D000010 25688
023 C000000 2397332
023 D000000 1985506
024 000000 N
025 D000001 0
025 D000002 0
025 D000003 0
025 D000004 0
025 D000005 0
025 D000006 0
025 D000007 0
025 D000008 0
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 A010000 70660
028 A020000 14137
028 A030000 0
028 A040000 132225
028 B010000 134280
028 B020000 12288
028 B030000 0
028 B040000 116002
028 C010000 176784
028 C020000 14119
028 C030000 0
028 C040000 158217
028 D010000 135670
028 D020000 12998
028 D030000 0
<PAGE> PAGE 4
028 D040000 184930
028 E010000 49346
028 E020000 12377
028 E030000 0
028 E040000 107125
028 F010000 96308
028 F020000 15737
028 F030000 0
028 F040000 130798
028 G010000 663048
028 G020000 81656
028 G030000 0
028 G040000 829297
028 H000000 642344
029 000000 Y
030 A000000 64
030 B000000 4.25
030 C000000 0.00
031 A000000 0
031 B000000 205
032 000000 0
033 000000 270
034 000000 Y
035 000000 3088
036 A000000 N
036 B000000 0
037 000000 N
038 000000 0
039 000000 N
040 000000 Y
041 000000 Y
042 A000000 0
042 B000000 0
042 C000000 100
042 D000000 0
042 E000000 0
042 F000000 0
042 G000000 0
042 H000000 0
043 000000 38917
044 000000 0
045 000000 Y
046 000000 N
047 000000 Y
048 000000 0.000
048 A010000 1000000
048 A020000 0.500
048 B010000 500000
048 B020000 0.475
048 C010000 500000
048 C020000 0.450
<PAGE> PAGE 5
048 D010000 500000
048 D020000 0.425
048 E010000 2500000
048 E020000 0.400
048 F010000 2500000
048 F020000 0.375
048 G010000 2500000
048 G020000 0.350
048 H010000 2500000
048 H020000 0.325
048 I010000 0
048 I020000 0.000
048 J010000 0
048 J020000 0.000
048 K010000 12500000
048 K020000 0.300
049 000000 N
050 000000 N
051 000000 N
052 000000 N
053 A000000 N
054 A000000 Y
054 B000000 Y
054 C000000 Y
054 D000000 N
054 E000000 N
054 F000000 N
054 G000000 Y
054 H000000 Y
054 I000000 N
054 J000000 Y
054 K000000 N
054 L000000 Y
054 M000000 Y
054 N000000 N
054 O000000 N
055 A000000 N
055 B000000 N
056 000000 Y
057 000000 N
058 A000000 N
059 000000 Y
060 A000000 Y
060 B000000 Y
061 000000 1000
062 A000000 Y
062 B000000 0.0
062 C000000 0.0
062 D000000 0.0
062 E000000 0.0
062 F000000 0.0
<PAGE> PAGE 6
062 G000000 0.0
062 H000000 0.0
062 I000000 0.0
062 J000000 0.0
062 K000000 0.0
062 L000000 0.0
062 M000000 25.1
062 N000000 75.7
062 O000000 0.0
062 P000000 0.0
062 Q000000 0.0
062 R000000 0.0
063 A000000 0
063 B000000 5.4
064 A000000 Y
064 B000000 N
066 A000000 N
067 000000 N
068 A000000 N
068 B000000 N
069 000000 N
070 A010000 N
070 A020000 N
070 B010000 N
070 B020000 N
070 C010000 N
070 C020000 N
070 D010000 N
070 D020000 N
070 E010000 N
070 E020000 N
070 F010000 N
070 F020000 N
070 G010000 N
070 G020000 N
070 H010000 N
070 H020000 N
070 I010000 N
070 I020000 N
070 J010000 N
070 J020000 N
070 K010000 N
070 K020000 N
070 L010000 N
070 L020000 N
070 M010000 N
070 M020000 N
070 N010000 N
070 N020000 N
070 O010000 Y
070 O020000 Y
<PAGE> PAGE 7
070 P010000 Y
070 P020000 N
070 Q010000 N
070 Q020000 N
070 R010000 N
070 R020000 N
071 A000000 717875
071 B000000 1347283
071 C000000 5038855
071 D000000 14
072 A000000 12
072 B000000 376888
072 C000000 0
072 D000000 0
072 E000000 0
072 F000000 22608
072 G000000 0
072 H000000 0
072 I000000 3543
072 J000000 845
072 K000000 0
072 L000000 185
072 M000000 20
072 N000000 61
072 O000000 0
072 P000000 0
072 Q000000 0
072 R000000 62
072 S000000 5
072 T000000 38917
072 U000000 0
072 V000000 0
072 W000000 65
072 X000000 66311
072 Y000000 0
072 Z000000 310577
072AA000000 0
072BB000000 2384
072CC010000 54570
072CC020000 0
072DD010000 309031
072DD020000 1545
072EE000000 0
073 A010000 0.0000
073 A020000 0.0000
073 B000000 0.0000
073 C000000 0.0000
074 A000000 157
074 B000000 0
074 C000000 0
074 D000000 5132755
<PAGE> PAGE 8
074 E000000 0
074 F000000 0
074 G000000 0
074 H000000 0
074 I000000 0
074 J000000 0
074 K000000 0
074 L000000 34357
074 M000000 81
074 N000000 5167350
074 O000000 49253
074 P000000 5238
074 Q000000 0
074 R010000 0
074 R020000 0
074 R030000 0
074 R040000 20655
074 S000000 0
074 T000000 5092204
074 U010000 549684
074 U020000 4067
074 V010000 0.00
074 V020000 0.00
074 W000000 0.0000
074 X000000 223999
074 Y000000 103525
075 A000000 0
075 B000000 5228747
076 000000 0.00
077 A000000 Y
077 B000000 Y
077 C000000 N
077 D000000 N
077 E000000 N
077 F000000 N
077 G000000 N
077 H000000 N
077 I000000 N
077 J000000 N
077 K000000 N
077 L000000 N
077 M000000 N
077 N000000 N
077 O000000 N
077 P000000 N
077 Q010000 N
077 Q020000 N
077 Q030000 N
078 000000 N
080 A000000 ICI MUTUAL INSURANCE CO.
080 B000000 GULF, VIGILANT, RELIANCE, CHUBB
<PAGE> PAGE 9
080 C000000 110000
081 A000000 Y
081 B000000 118
082 A000000 N
082 B000000 0
083 A000000 N
083 B000000 0
084 A000000 N
084 B000000 0
085 A000000 Y
085 B000000 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
SIGNATURE BARRY FINK
TITLE VICE PRESIDENT
WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
MORGAN STANLEY DEAN WITTER U.S.
GOVERNMENT SECURITIES TRUST- CLASS D
ANNUAL FDS
12-31-1998
</LEGEND>
<CIK> 0000730044
<NAME> MSDW U.S. GOVERNMENT SECURITIES TRUST - CLASS D
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 4,816,826,788
<INVESTMENTS-AT-VALUE> 5,132,755,149
<RECEIVABLES> 34,356,806
<ASSETS-OTHER> 80,247
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 5,167,349,543
<PAYABLE-FOR-SECURITIES> 49,253,125
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 25,892,699
<TOTAL-LIABILITIES> 75,145,824
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 5,694,016,539
<SHARES-COMMON-STOCK> 2,221,111
<SHARES-COMMON-PRIOR> 1,248,136
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (917,741,181)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 315,928,361
<NET-ASSETS> 20,391,766
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 376,887,864
<OTHER-INCOME> 0
<EXPENSES-NET> 66,311,298
<NET-INVESTMENT-INCOME> 310,576,566
<REALIZED-GAINS-CURRENT> (2,384,102)
<APPREC-INCREASE-CURRENT> 54,569,658
<NET-CHANGE-FROM-OPS> 362,762,122
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (944,519)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 1,554,909
<NUMBER-OF-SHARES-REDEEMED> (1,666,314)
<SHARES-REINVESTED> 97,395
<NET-CHANGE-IN-ASSETS> (373,212,575)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (1,024,088,069)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 22,607,800
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 66,311,298
<AVERAGE-NET-ASSETS> 14,304,912
<PER-SHARE-NAV-BEGIN> 9.11
<PER-SHARE-NII> 0.61
<PER-SHARE-GAIN-APPREC> 0.07
<PER-SHARE-DIVIDEND> (0.61)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 9.18
<EXPENSE-RATIO> 0.52
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
MORGAN STANLEY DEAN WITTER U.S.
GOVERNMENT SECURITIES TRUST- CLASS C
ANNUAL FDS
12-31-1998
</LEGEND>
<CIK> 0000730044
<NAME> MSDW U.S. GOVERNMENT SECURITIES TRUST - CLASS C
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 4,816,826,788
<INVESTMENTS-AT-VALUE> 5,132,755,149
<RECEIVABLES> 34,356,806
<ASSETS-OTHER> 80,247
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 5,167,349,543
<PAYABLE-FOR-SECURITIES> 49,253,125
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 25,892,699
<TOTAL-LIABILITIES> 75,145,824
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 5,694,016,539
<SHARES-COMMON-STOCK> 1,846,174
<SHARES-COMMON-PRIOR> 478,135
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (917,741,181)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 315,928,361
<NET-ASSETS> 17,086,723
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 376,887,864
<OTHER-INCOME> 0
<EXPENSES-NET> 66,311,298
<NET-INVESTMENT-INCOME> 310,576,566
<REALIZED-GAINS-CURRENT> (2,384,102)
<APPREC-INCREASE-CURRENT> 54,569,658
<NET-CHANGE-FROM-OPS> 362,762,122
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (600,619)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 4,818,849
<NUMBER-OF-SHARES-REDEEMED> (3,492,672)
<SHARES-REINVESTED> 41,862
<NET-CHANGE-IN-ASSETS> (373,212,575)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (1,024,088,069)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 22,607,800
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 66,311,298
<AVERAGE-NET-ASSETS> 10,316,426
<PER-SHARE-NAV-BEGIN> 9.17
<PER-SHARE-NII> 0.55
<PER-SHARE-GAIN-APPREC> 0.09
<PER-SHARE-DIVIDEND> (0.55)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 9.26
<EXPENSE-RATIO> 1.27
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
MORGAN STANLEY DEAN WITTER U.S.
GOVERNMENT SECURITIES TRUST- CLASS B
ANNUAL FDS
12-31-1998
</LEGEND>
<CIK> 0000730044
<NAME> MSDW U.S. GOVERNMENT SECURITIES TRUST-CLASS B
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 4,816,826,788
<INVESTMENTS-AT-VALUE> 5,132,755,149
<RECEIVABLES> 34,356,806
<ASSETS-OTHER> 80,247
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 5,167,349,543
<PAYABLE-FOR-SECURITIES> 49,253,125
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 25,892,699
<TOTAL-LIABILITIES> 75,145,824
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 5,694,016,539
<SHARES-COMMON-STOCK> 543,307,518
<SHARES-COMMON-PRIOR> 596,277,853
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (917,741,181)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 315,928,361
<NET-ASSETS> 4,996,187,325
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 376,887,864
<OTHER-INCOME> 0
<EXPENSES-NET> 66,311,298
<NET-INVESTMENT-INCOME> 310,576,566
<REALIZED-GAINS-CURRENT> (2,384,102)
<APPREC-INCREASE-CURRENT> 54,569,658
<NET-CHANGE-FROM-OPS> 362,769,122
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (306,635,357)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 103,474,883
<NUMBER-OF-SHARES-REDEEMED> (173,896,303)
<SHARES-REINVESTED> 17,451,085
<NET-CHANGE-IN-ASSETS> (373,212,575)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (1,024,088,069)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 22,607,800
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 66,311,298
<AVERAGE-NET-ASSETS> 5,166,525,982
<PER-SHARE-NAV-BEGIN> 9.10
<PER-SHARE-NII> 0.54
<PER-SHARE-GAIN-APPREC> 0.10
<PER-SHARE-DIVIDEND> (0.54)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 9.20
<EXPENSE-RATIO> 1.27
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
MORGAN STANLEY DEAN WITTER U.S.
GOVERNMENT SECURITIES TRUST- CLASS A
ANNUAL FDS
12-31-1998
</LEGEND>
<CIK> 0000730044
<NAME> MSDW U.S. GOVERNMENT SEC TRUST - CLASS A
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 4,816,826,788
<INVESTMENTS-AT-VALUE> 5,132,755,149
<RECEIVABLES> 34,356,806
<ASSETS-OTHER> 80,247
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 5,167,349,543
<PAYABLE-FOR-SECURITIES> 49,253,125
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 25,892,699
<TOTAL-LIABILITIES> 75,145,824
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 5,694,016,539
<SHARES-COMMON-STOCK> 6,376,543
<SHARES-COMMON-PRIOR> 2,292,255
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (917,741,181)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 315,928,361
<NET-ASSETS> 58,537,905
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 376,887,864
<OTHER-INCOME> 0
<EXPENSES-NET> 66,311,298
<NET-INVESTMENT-INCOME> 310,576,566
<REALIZED-GAINS-CURRENT> (2,384,102)
<APPREC-INCREASE-CURRENT> 54,569,658
<NET-CHANGE-FROM-OPS> 362,762,122
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (2,396,071)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 4,837,972
<NUMBER-OF-SHARES-REDEEMED> (898,895)
<SHARES-REINVESTED> 145,211
<NET-CHANGE-IN-ASSETS> (373,212,575)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (1,024,088,069)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 22,607,800
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 66,311,298
<AVERAGE-NET-ASSETS> 37,599,477
<PER-SHARE-NAV-BEGIN> 9.09
<PER-SHARE-NII> 0.59
<PER-SHARE-GAIN-APPREC> 0.09
<PER-SHARE-DIVIDEND> (0.59)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 9.18
<EXPENSE-RATIO> 0.77
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
