<PAGE> PAGE 1
000 A000000 03/31/99
000 C000000 0000912492
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 3.0
000 J000000 U
001 A000000 DREYFUS INSTITUTIONAL SHORT TERM TREAS FUND
001 B000000 811-07097
001 C000000 2129226764
002 A000000 200 PARK AVENUE
002 B000000 NEW YORK
002 C000000 NY
002 D010000 10166
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 N
007 B000000 0
015 A000001 MELLON BANK, N.A.
015 B000001 C
015 C010001 PITTSBURGH
015 C020001 PA
015 C030001 15258
015 E030001 X
018 000000 Y
019 A000000 Y
019 B000000 161
019 C000000 DREYFUSFAM
022 A000001 UBS AG G. LANSTON & CO. INC.
022 B000001 13-2932996
022 C000001 537422
022 D000001 0
022 A000002 MERRILL LYNCH, PIERCE, FENNER & SMITH INC.
022 B000002 13-5674085
022 C000002 148940
022 D000002 133880
022 A000003 LEHMAN BROTHERS INC.
022 B000003 13-2518466
022 C000003 37192
022 D000003 67661
022 A000004 CS FIRST BOSTON CORPORATION
022 B000004 13-5659485
022 C000004 40008
022 D000004 28278
022 A000005 GOLDMAN, SACHS & CO.
022 B000005 13-5108880
022 C000005 42156
<PAGE> PAGE 2
022 D000005 18463
022 A000006 SALOMON SMITH BARNEY
022 B000006 13-1912900
022 C000006 25435
022 D000006 34474
022 A000007 BARCLAYS DE ZOETE WEDD SECURITIES, INC.
022 B000007 13-3551367
022 C000007 31214
022 D000007 0
022 A000008 DAIWA SECURITIES AMERCIA INC.
022 B000008 13-5680329
022 C000008 16017
022 D000008 4955
022 A000009 GREENWICH CAPITAL MARKETS, INC.
022 B000009 13-3172275
022 C000009 0
022 D000009 20946
022 A000010 BEAR, STEARNS & CO. INC.
022 B000010 13-3299429
022 C000010 11600
022 D000010 0
023 C000000 893661
023 D000000 319137
024 000000 Y
025 A000001 BEAR, STEARNS & CO. INC.
025 B000001 13-3299429
025 C000001 D
025 D000001 3000
025 D000002 0
025 D000003 0
025 D000004 0
025 D000005 0
025 D000006 0
025 D000007 0
025 D000008 0
028 A010000 2861
028 A020000 186
028 A030000 0
028 A040000 2091
028 B010000 862
028 B020000 208
028 B030000 0
028 B040000 7116
028 C010000 1159
028 C020000 199
028 C030000 0
028 C040000 1629
028 D010000 3755
028 D020000 185
028 D030000 0
028 D040000 1445
<PAGE> PAGE 3
028 E010000 1182
028 E020000 183
028 E030000 0
028 E040000 191
028 F010000 788
028 F020000 206
028 F030000 0
028 F040000 6158
028 G010000 10607
028 G020000 1167
028 G030000 0
028 G040000 18630
028 H000000 0
042 A000000 1
042 B000000 0
042 C000000 99
042 D000000 0
042 E000000 0
042 F000000 0
042 G000000 0
042 H000000 0
043 000000 14
044 000000 0
053 A000000 N
055 A000000 Y
055 B000000 Y
056 000000 N
057 000000 N
062 A000000 Y
062 B000000 0.0
062 C000000 0.0
062 D000000 4.4
062 E000000 0.0
062 F000000 0.0
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 100.3
062 N000000 0.0
062 O000000 0.0
062 P000000 0.0
062 Q000000 0.0
062 R000000 0.0
063 A000000 0
063 B000000 1.7
064 A000000 Y
064 B000000 N
066 A000000 N
<PAGE> PAGE 4
067 000000 N
068 A000000 N
068 B000000 N
069 000000 N
070 A010000 Y
070 A020000 Y
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 Y
070 K020000 N
070 L010000 N
070 L020000 N
070 M010000 N
070 M020000 N
070 N010000 Y
070 N020000 N
070 O010000 Y
070 O020000 Y
070 P010000 Y
070 P020000 N
070 Q010000 N
070 Q020000 N
070 R010000 N
070 R020000 N
071 A000000 309388
071 B000000 315111
071 C000000 72469
071 D000000 427
072 A000000 6
072 B000000 2055
072 C000000 0
072 D000000 0
072 E000000 0
072 F000000 73
072 G000000 0
<PAGE> PAGE 5
072 H000000 0
072 I000000 0
072 J000000 0
072 K000000 0
072 L000000 0
072 M000000 0
072 N000000 0
072 O000000 0
072 P000000 0
072 Q000000 0
072 R000000 0
072 S000000 0
072 T000000 14
072 U000000 0
072 V000000 0
072 W000000 0
072 X000000 87
072 Y000000 0
072 Z000000 1968
072AA000000 854
072BB000000 603
072CC010000 0
072CC020000 1219
072DD010000 1681
072DD020000 287
072EE000000 0
073 A010000 0.0544
073 A020000 0.0523
073 B000000 0.0000
073 C000000 0.0000
074 A000000 0
074 B000000 3000
074 C000000 67802
074 D000000 0
074 E000000 0
074 F000000 0
074 G000000 0
074 H000000 0
074 I000000 0
074 J000000 13975
074 K000000 0
074 L000000 586
074 M000000 0
074 N000000 85363
074 O000000 7986
074 P000000 13
074 Q000000 0
074 R010000 0
074 R020000 0
074 R030000 0
074 R040000 9728
<PAGE> PAGE 6
074 S000000 0
074 T000000 67636
074 U010000 28652
074 U020000 5394
074 V010000 1.98
074 V020000 2.00
074 W000000 0.0000
074 X000000 125
074 Y000000 0
075 A000000 0
075 B000000 61715
076 000000 0.00
077 A000000 Y
080 A000000 VIGILANT INSURANCE COMPANY
080 B000000 NATIONAL UNION FIRE INSURANCE COMPANY
080 C000000 125000
081 A000000 Y
081 B000000 182
082 A000000 N
082 B000000 0
083 A000000 N
083 B000000 0
084 A000000 N
084 B000000 0
085 A000000 Y
085 B000000 N
SIGNATURE MICHAEL S. PETRUCELLI
TITLE V.P & ASST TREASURER
WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000912492
<NAME> DREYFUS INSTITUTIONAL SHORT TERM TREASURY FUND
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> SEP-30-1999
<PERIOD-END> MAR-31-1999
<INVESTMENTS-AT-COST> 71137
<INVESTMENTS-AT-VALUE> 70802
<RECEIVABLES> 14561
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 85362
<PAYABLE-FOR-SECURITIES> 7986
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 9741
<TOTAL-LIABILITIES> 17727
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 70532
<SHARES-COMMON-STOCK> 28652
<SHARES-COMMON-PRIOR> 32408
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (2561)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> (335)
<NET-ASSETS> 56864
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 2055
<OTHER-INCOME> 0
<EXPENSES-NET> 87
<NET-INVESTMENT-INCOME> 1968
<REALIZED-GAINS-CURRENT> 251
<APPREC-INCREASE-CURRENT> (1219)
<NET-CHANGE-FROM-OPS> 1000
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (1681)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 2969
<NUMBER-OF-SHARES-REDEEMED> (7197)
<SHARES-REINVESTED> 471
<NET-CHANGE-IN-ASSETS> (7824)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2811)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 73
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 87
<AVERAGE-NET-ASSETS> 61715
<PER-SHARE-NAV-BEGIN> 2.01
<PER-SHARE-NII> .05
<PER-SHARE-GAIN-APPREC> (0.03)
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> (.05)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.98
<EXPENSE-RATIO> .002
[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
<CIK> 0000912492
<NAME> DREYFUS INSTITUTIONAL SHORT TERM TREASURY FUND
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> SEP-30-1999
<PERIOD-END> MAR-31-1999
<INVESTMENTS-AT-COST> 71137
<INVESTMENTS-AT-VALUE> 70802
<RECEIVABLES> 14561
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 85363
<PAYABLE-FOR-SECURITIES> 7986
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 9741
<TOTAL-LIABILITIES> 17727
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 70532
<SHARES-COMMON-STOCK> 5394
<SHARES-COMMON-PRIOR> 5087
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (2561)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> (335)
<NET-ASSETS> 10772
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 2055
<OTHER-INCOME> 0
<EXPENSES-NET> 87
<NET-INVESTMENT-INCOME> 1968
<REALIZED-GAINS-CURRENT> 251
<APPREC-INCREASE-CURRENT> (1219)
<NET-CHANGE-FROM-OPS> 1000
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (287)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 2324
<NUMBER-OF-SHARES-REDEEMED> (2131)
<SHARES-REINVESTED> 113
<NET-CHANGE-IN-ASSETS> (7824)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2811)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 73
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 87
<AVERAGE-NET-ASSETS> 11049
<PER-SHARE-NAV-BEGIN> 2.02
<PER-SHARE-NII> .05
<PER-SHARE-GAIN-APPREC> (0.02)
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> (.05)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 2.00
<EXPENSE-RATIO> .005
[AVG-DEBT-OUTSTANDING] 0
[AVG-DEBT-PER-SHARE] 0
</TABLE>