<PAGE> PAGE 1
000 B000000 09/30/99
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 2129226832
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
018 000000 Y
019 A000000 Y
019 B000000 162
019 C000000 DREYFUSFAM
022 A000001 UBS AG
022 B000001 13-2932996
022 C000001 839272
022 D000001 0
022 A000002 MERRILL LYNCH, PIERCE, FENNER & SMITH INC.
022 B000002 13-5674085
022 C000002 320926
022 D000002 319371
022 A000003 GOLDMAN, SACHS & CO.
022 B000003 13-5108880
022 C000003 148251
022 D000003 18972
022 A000004 LEHMAN BROTHERS INC.
022 B000004 13-2518466
022 C000004 38192
022 D000004 67661
022 A000005 DONALDSON, LUFKIN & JENRETTE SECURITIES CORP.
022 B000005 13-2741729
022 C000005 89904
022 D000005 0
022 A000006 BEAR, STEARNS & CO. INC.
022 B000006 13-3299429
022 C000006 70521
022 D000006 0
022 A000007 CS FIRST BOSTON CORPORATION
<PAGE> PAGE 2
022 B000007 13-5659485
022 C000007 40008
022 D000007 22206
022 A000008 BARCLAYS DE ZOETE WEDD SECURITIES, INC.
022 B000008 13-3551367
022 C000008 48319
022 D000008 0
022 A000009 SALOMON SMITH BARNEY
022 B000009 13-1912900
022 C000009 25435
022 D000009 20543
022 A000010 DAIWA SECURITIES AMERICA, INC.
022 B000010 13-5680329
022 C000010 16017
022 D000010 4955
023 C000000 1654348
023 D000000 536248
025 A000001 UBS AG
025 B000001 13-2932996
025 C000001 D
025 D000001 1200
025 D000002 0
025 D000003 0
025 D000004 0
025 D000005 0
025 D000006 0
025 D000007 0
025 D000008 0
028 A010000 1532
028 A020000 151
028 A030000 0
028 A040000 3918
028 B010000 762
028 B020000 126
028 B030000 0
028 B040000 7255
028 C010000 454
028 C020000 151
028 C030000 0
028 C040000 3487
028 D010000 3391
028 D020000 144
028 D030000 0
028 D040000 5702
028 E010000 1548
028 E020000 141
028 E030000 0
028 E040000 6010
028 F010000 3754
028 F020000 132
028 F030000 0
<PAGE> PAGE 3
028 F040000 6393
028 G010000 11441
028 G020000 845
028 G030000 0
028 G040000 32765
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 30
044 000000 0
062 A000000 Y
062 B000000 12.5
062 C000000 0.0
062 D000000 2.6
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 83.3
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 1.9
064 A000000 Y
064 B000000 N
071 A000000 466248
071 B000000 500457
071 C000000 56648
071 D000000 823
072 A000000 12
072 B000000 3621
072 C000000 0
072 D000000 0
072 E000000 0
072 F000000 129
072 G000000 0
072 H000000 0
072 I000000 0
<PAGE> PAGE 4
072 J000000 0
072 K000000 0
072 L000000 0
072 M000000 0
072 N000000 0
072 O000000 0
072 P000000 1
072 Q000000 0
072 R000000 0
072 S000000 0
072 T000000 30
072 U000000 0
072 V000000 0
072 W000000 0
072 X000000 160
072 Y000000 0
072 Z000000 3461
072AA000000 848
072BB000000 1453
072CC010000 0
072CC020000 1016
072DD010000 2849
072DD020000 612
072EE000000 0
073 A010000 0.1071
073 A020000 0.1028
073 B000000 0.0000
073 C000000 0.0000
074 A000000 237
074 B000000 1200
074 C000000 5829
074 D000000 38734
074 E000000 0
074 F000000 0
074 G000000 0
074 H000000 0
074 I000000 0
074 J000000 0
074 K000000 0
074 L000000 523
074 M000000 0
074 N000000 46523
074 O000000 0
074 P000000 8
074 Q000000 0
074 R010000 0
074 R020000 0
074 R030000 0
074 R040000 12
074 S000000 0
074 T000000 46503
<PAGE> PAGE 5
074 U010000 16225
074 U020000 7415
074 V010000 1.96
074 V020000 1.97
074 W000000 0.0000
074 X000000 121
074 Y000000 0
075 A000000 0
075 B000000 52835
076 000000 0.00
077 A000000 Y
077 B000000 Y
077 Q010000 N
080 A000000 VIGILANT INSURANCE COMPANY
080 B000000 NATIONAL UNION FIRE INSURANCE COMPANY
080 C000000 125000
081 A000000 Y
081 B000000 180
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 STEPHANIE D. PIERCE
TITLE VP,ASST SECY.& TREAS
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
<SERIES>
<NUMBER> 001
<NAME> INSTITUTIONAL SHARES
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> SEP-30-1999
<PERIOD-END> SEP-30-1999
<INVESTMENTS-AT-COST> 45896
<INVESTMENTS-AT-VALUE> 45763
<RECEIVABLES> 523
<ASSETS-OTHER> 237
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 46523
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 20
<TOTAL-LIABILITIES> 20
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 50052
<SHARES-COMMON-STOCK> 16225
<SHARES-COMMON-PRIOR> 32408
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (3416)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> (133)
<NET-ASSETS> 31860
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 3621
<OTHER-INCOME> 0
<EXPENSES-NET> 160
<NET-INVESTMENT-INCOME> 3461
<REALIZED-GAINS-CURRENT> (605)
<APPREC-INCREASE-CURRENT> (1016)
<NET-CHANGE-FROM-OPS> 1840
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (2849)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 5643
<NUMBER-OF-SHARES-REDEEMED> (22601)
<SHARES-REINVESTED> 775
<NET-CHANGE-IN-ASSETS> (28956)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2811)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 129
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 160
<AVERAGE-NET-ASSETS> 52835
<PER-SHARE-NAV-BEGIN> 2.01
<PER-SHARE-NII> .11
<PER-SHARE-GAIN-APPREC> (0.05)
<PER-SHARE-DIVIDEND> (.11)
<PER-SHARE-DISTRIBUTIONS> .00
<RETURNS-OF-CAPITAL> .000
<PER-SHARE-NAV-END> 1.96
<EXPENSE-RATIO> .002
[AVG-DEBT-OUTSTANDING] 000
[AVG-DEBT-PER-SHARE] 000
</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
<SERIES>
<NUMBER> 002
<NAME> INVESTOR SHARES
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> SEP-30-1999
<PERIOD-END> SEP-30-1999
<INVESTMENTS-AT-COST> 45896
<INVESTMENTS-AT-VALUE> 45763
<RECEIVABLES> 523
<ASSETS-OTHER> 237
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 46523
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 20
<TOTAL-LIABILITIES> 20
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 50052
<SHARES-COMMON-STOCK> 7415
<SHARES-COMMON-PRIOR> 5087
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (3416)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> (133)
<NET-ASSETS> 14643
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 3621
<OTHER-INCOME> 0
<EXPENSES-NET> 160
<NET-INVESTMENT-INCOME> 3461
<REALIZED-GAINS-CURRENT> (605)
<APPREC-INCREASE-CURRENT> (1016)
<NET-CHANGE-FROM-OPS> 1840
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (612)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 5447
<NUMBER-OF-SHARES-REDEEMED> (3357)
<SHARES-REINVESTED> 238
<NET-CHANGE-IN-ASSETS> (28956)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2811)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 129
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 160
<AVERAGE-NET-ASSETS> 11867
<PER-SHARE-NAV-BEGIN> 2.02
<PER-SHARE-NII> .10
<PER-SHARE-GAIN-APPREC> (.05)
<PER-SHARE-DIVIDEND> (.10)
<PER-SHARE-DISTRIBUTIONS> .00
<RETURNS-OF-CAPITAL> .000
<PER-SHARE-NAV-END> 1.97
<EXPENSE-RATIO> .005
[AVG-DEBT-OUTSTANDING] 000
[AVG-DEBT-PER-SHARE] 000
</TABLE>
Report of Independent Auditors
To the Shareholders and Board of Directors of
Dreyfus Institutional Short-Term Treasury Fund
In planning and performing our audit of the financial statements of Dreyfus
Institutional Short-Term Treasury Fund for the year ended September 30,
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, not to provide assurance on
internal control.
The management of Dreyfus Institutional Short-Term Treasury 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 internal control, error 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 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 internal control and its
operation, including controls for safeguarding securities, that we consider
to be material weaknesses as defined above at September 30, 1999.
This report is intended solely for the information and use of management,
the Board of Directors of Dreyfus Institutional Short-Term Treasury Fund,
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
November 1, 1999
