<PAGE> PAGE 1
000 B000000 05/31/97
000 C000000 0000939934
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 3.0.a
000 J000000 U
001 A000000 SEI INSTITUTIONAL INVESTMENTS TRUST
001 B000000 811-7257
001 C000000 8003425734
002 A000000 2 OLIVER STREET
002 B000000 BOSTON
002 C000000 MA
002 D010000 02109
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 Y
007 B000000 4
020 A000001 WAKO INTERNATIONAL
020 C000001 493
020 A000002 INSTINET
020 B000002 13-3443995
020 C000002 295
020 A000003 YAMAICHI
020 C000003 205
020 A000004 JAMES CAPEL
020 B000004 52-1348224
020 C000004 143
020 A000005 J.P. MORGAN
020 B000005 13-3224016
020 C000005 110
020 A000006 SALOMON BROTHERS
020 B000006 13-3082694
020 C000006 78
020 A000007 MERRILL LYNCH
020 B000007 13-5674085
020 C000007 68
020 A000008 HOENIG
020 C000008 54
020 A000009 SBC WARBURG
020 C000009 37
020 A000010 SMITH BARNEY
020 B000010 13-2518466
020 C000010 34
021 000000 2635
022 A000001 MERRILL LYNCH
022 B000001 13-5674085
<PAGE> PAGE 2
022 C000001 4128181
022 D000001 267566
022 A000002 J.P. MORGAN
022 B000002 13-3224016
022 C000002 1213435
022 D000002 48080
022 A000003 LEHMAN BROTHERS
022 B000003 13-2927667
022 C000003 1680649
022 D000003 135654
022 A000004 MORGAN STANLEY
022 B000004 13-2655998
022 C000004 109809
022 D000004 82530
022 A000005 MORGAN GRENFELL
022 C000005 70098
022 D000005 122
022 A000006 PAINE WEBBER
022 B000006 13-2760086
022 C000006 63910
022 D000006 23689
022 A000007 GOLDMAN SACHS
022 B000007 13-5108880
022 C000007 58242
022 D000007 40699
022 A000008 FARRELL WAKO
022 C000008 54168
022 D000008 0
022 A000009 SALOMON BROTHERS
022 B000009 13-3082694
022 C000009 47972
022 D000009 23761
022 A000010 MCDONALD & CO
022 B000010 34-0642435
022 C000010 28216
022 D000010 26855
023 C000000 8316150
023 D000000 1030391
077 A000000 Y
080 A00AA00 CONTINENTAL CASUALTY
080 C00AA00 46000
081 A00AA00 Y
081 B00AA00 250
082 A00AA00 Y
082 B00AA00 50
083 A00AA00 N
083 B00AA00 0
084 A00AA00 N
084 B00AA00 0
085 A00AA00 Y
085 B00AA00 N
<PAGE> PAGE 3
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
024 000100 Y
025 A000101 LEHMAN BROTHERS
025 B000101 13-2927667
025 C000101 E
025 D000101 908
025 A000102 MERRILL LYNCH
025 B000102 13-5674085
025 C000102 E
025 D000102 3509
025 A000103 MERRILL LYNCH
025 B000103 13-5674085
025 C000103 D
025 D000103 4014
025 A000104 J.P. MORGAN
025 B000104 13-3224016
025 C000104 E
025 D000104 1836
025 A000105 SALOMON BROTHERS
025 B000105 13-3082694
025 C000105 E
025 D000105 402
025 D000106 0
025 D000107 0
025 D000108 0
062 A000100 N
062 B000100 0.0
062 C000100 0.0
062 D000100 0.0
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 0.0
062 N000100 0.0
062 O000100 0.0
<PAGE> PAGE 4
062 P000100 0.0
062 Q000100 0.0
062 R000100 0.0
071 A000100 552462
071 B000100 199688
071 C000100 281884
071 D000100 71
072 A000100 12
074 N000100 438818
074 T000100 438818
075 A000100 0
075 B000100 289775
025 A000201 MERRILL LYNCH
025 B000201 13-5674085
025 C000201 D
025 D000201 8868
025 D000202 0
025 D000203 0
025 D000204 0
025 D000205 0
025 D000206 0
025 D000207 0
025 D000208 0
062 A000200 N
062 B000200 0.0
062 C000200 0.0
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 0.0
062 R000200 0.0
071 A000200 215351
071 B000200 106602
071 C000200 65421
071 D000200 163
072 A000200 12
074 N000200 128298
074 T000200 123941
075 A000200 0
075 B000200 77917
025 A000301 J.P. MORGAN
<PAGE> PAGE 5
025 B000301 13-3224016
025 C000301 E
025 D000301 198
025 A000302 LEHMAN BROTHERS
025 B000302 13-2927667
025 C000302 E
025 D000302 3224
025 A000303 LEHMAN BROTHERS
025 B000303 13-2927667
025 C000303 D
025 D000303 889
025 A000304 MERRILL LYNCH
025 B000304 13-5674085
025 C000304 E
025 D000304 1568
025 A000305 MERRILL LYNCH
025 B000305 13-5674085
025 C000305 D
025 D000305 5872
025 A000306 PAINE WEBBER
025 B000306 13-2760086
025 C000306 D
025 D000306 464
025 A000307 SALOMON BROTHERS
025 B000307 13-3082694
025 C000307 E
025 D000307 1257
025 D000308 0
062 A000300 Y
062 B000300 0.0
062 C000300 1.4
062 D000300 15.1
062 E000300 0.0
062 F000300 0.0
062 G000300 0.0
062 H000300 0.0
062 I000300 2.0
062 J000300 0.0
062 K000300 0.0
062 L000300 0.0
062 M000300 30.0
062 N000300 21.8
062 O000300 0.0
062 P000300 18.8
062 Q000300 11.9
062 R000300 0.0
071 A000300 602588
071 B000300 323929
071 C000300 166869
071 D000300 194
072 A000300 12
<PAGE> PAGE 6
074 N000300 378671
074 O000300 26734
074 P000300 0
074 Q000300 0
074 R010300 0
074 R020300 0
074 R030300 0
074 R040300 2633
074 S000300 0
074 T000300 349304
074 U010300 34494
074 U020300 0
074 V010300 10.13
074 V020300 0.00
074 W000300 0.0000
074 X000300 7
074 Y000300 0
075 A000300 0
075 B000300 195858
008 A000701 ACADIAN ASSET MANAGEMENT
008 B000701 S
008 C000701 801-0000
008 D010701 BOSTON
008 D020701 MA
008 D030701 02110
008 A000702 FARRELL WAKO GLOBAL INVESTMENT
008 B000702 S
008 C000702 801-0000
008 D010702 NEW YORK
008 D020702 NY
008 D030702 10017
008 A000703 LAZARD LONDON INTERNATIONAL INVESTMENT MGMT
008 B000703 S
008 C000703 801-0000
008 D010703 LONDON
008 D050703 UNITED KINGDOM
008 D060703 EC2M1NB
024 000700 N
062 A000700 N
062 B000700 0.0
062 C000700 0.0
062 D000700 0.0
062 E000700 0.0
062 F000700 0.0
062 G000700 0.0
062 H000700 0.0
062 I000700 0.0
062 J000700 0.0
062 K000700 0.0
062 L000700 0.0
062 M000700 0.0
<PAGE> PAGE 7
062 N000700 0.0
062 O000700 0.0
062 P000700 0.0
062 Q000700 0.0
062 R000700 0.0
071 A000700 678060
071 B000700 344248
071 C000700 308170
071 D000700 120
072 A000700 12
072 Y000700 546
072 Z000700 5073
072AA000700 4030
072BB000700 0
072CC010700 21723
072CC020700 0
072DD010700 1960
072DD020700 0
072EE000700 335
073 A010700 0.0530
073 A020700 0.0000
073 B000700 0.0092
073 C000700 0.0000
074 N000700 390389
074 T000700 384663
075 A000700 0
075 B000700 308170
SIGNATURE STEVE MEYER
TITLE CONTROLLER
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000939934
<NAME> SEI INSTITUTIONAL INVESTMENTS TRUST
<SERIES>
<NUMBER> 010
<NAME> LARGE CAP FUND
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> MAY-31-1997
<PERIOD-START> JUN-01-1996
<PERIOD-END> MAY-31-1997
<INVESTMENTS-AT-COST> 361649
<INVESTMENTS-AT-VALUE> 436635
<RECEIVABLES> 0
<ASSETS-OTHER> 2183
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 438818
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 0
<TOTAL-LIABILITIES> 0
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 358583
<SHARES-COMMON-STOCK> 34662
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 1080
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 3744
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 75411
<NET-ASSETS> 43818
<DIVIDEND-INCOME> 4849
<INTEREST-INCOME> 691
<OTHER-INCOME> 0
<EXPENSES-NET> (948)
<NET-INVESTMENT-INCOME> 4592
<REALIZED-GAINS-CURRENT> 3744
<APPREC-INCREASE-CURRENT> 75411
<NET-CHANGE-FROM-OPS> 83747
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (3512)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 41222
<NUMBER-OF-SHARES-REDEEMED> (6887)
<SHARES-REINVESTED> 327
<NET-CHANGE-IN-ASSETS> 438818
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 1117
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1471
<AVERAGE-NET-ASSETS> 195858
<PER-SHARE-NAV-BEGIN> 10.00
<PER-SHARE-NII> .17
<PER-SHARE-GAIN-APPREC> 2.63
<PER-SHARE-DIVIDEND> (.14)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 12.66
<EXPENSE-RATIO> .34
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000939934
<NAME> SEI INSTITUTIONAL INVESTMENTS TRUST
<SERIES>
<NUMBER> 020
<NAME> SMALL CAP FUND
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> MAY-31-1997
<PERIOD-START> JUN-01-1996
<PERIOD-END> MAY-31-1997
<INVESTMENTS-AT-COST> 121037
<INVESTMENTS-AT-VALUE> 128298
<RECEIVABLES> 0
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 128298
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4357
<TOTAL-LIABILITIES> 4357
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 112082
<SHARES-COMMON-STOCK> 11410
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 103
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 3933
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 7823
<NET-ASSETS> 123941
<DIVIDEND-INCOME> 521
<INTEREST-INCOME> 453
<OTHER-INCOME> 0
<EXPENSES-NET> (451)
<NET-INVESTMENT-INCOME> 523
<REALIZED-GAINS-CURRENT> 3933
<APPREC-INCREASE-CURRENT> 7823
<NET-CHANGE-FROM-OPS> 12279
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (420)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 12976
<NUMBER-OF-SHARES-REDEEMED> (1608)
<SHARES-REINVESTED> 42
<NET-CHANGE-IN-ASSETS> 123941
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 488
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 595
<AVERAGE-NET-ASSETS> 77917
<PER-SHARE-NAV-BEGIN> 10.00
<PER-SHARE-NII> .06
<PER-SHARE-GAIN-APPREC> .85
<PER-SHARE-DIVIDEND> (.05)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.86
<EXPENSE-RATIO> .60
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000939934
<NAME> SEI INSTITUTIONAL INVESTMENTS TRUST
<SERIES>
<NUMBER> 030
<NAME> CORE FIXED INCOME FUND
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> MAY-31-1997
<PERIOD-START> JUN-01-1996
<PERIOD-END> MAY-31-1997
<INVESTMENTS-AT-COST> 351944
<INVESTMENTS-AT-VALUE> 352873
<RECEIVABLES> 3834
<ASSETS-OTHER> 21964
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 378671
<PAYABLE-FOR-SECURITIES> 26734
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 2633
<TOTAL-LIABILITIES> 29367
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 348170
<SHARES-COMMON-STOCK> 34494
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 241
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 893
<NET-ASSETS> 349304
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 12834
<OTHER-INCOME> 0
<EXPENSES-NET> (396)
<NET-INVESTMENT-INCOME> 12438
<REALIZED-GAINS-CURRENT> 1013
<APPREC-INCREASE-CURRENT> 893
<NET-CHANGE-FROM-OPS> 14344
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (12438)
<DISTRIBUTIONS-OF-GAINS> (772)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 35991
<NUMBER-OF-SHARES-REDEEMED> (2780)
<SHARES-REINVESTED> 1283
<NET-CHANGE-IN-ASSETS> 349205
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 566
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 798
<AVERAGE-NET-ASSETS> 289775
<PER-SHARE-NAV-BEGIN> 10.00
<PER-SHARE-NII> .64
<PER-SHARE-GAIN-APPREC> .17
<PER-SHARE-DIVIDEND> (.64)
<PER-SHARE-DISTRIBUTIONS> (.04)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.13
<EXPENSE-RATIO> .21
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000939934
<NAME> SEI INSTITUTIONAL INVESTMENTS TRUST
<SERIES>
<NUMBER> 041
<NAME> INTERNATIONAL EQUITY
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> MAY-31-1997
<PERIOD-START> JUN-14-1996
<PERIOD-END> MAY-31-1997
<INVESTMENTS-AT-COST> 360933
<INVESTMENTS-AT-VALUE> 382171
<RECEIVABLES> 5157
<ASSETS-OTHER> 3061
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 390389
<PAYABLE-FOR-SECURITIES> 1832
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 3894
<TOTAL-LIABILITIES> 5726
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 356132
<SHARES-COMMON-STOCK> 35987
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 2632
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 4176
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 21723
<NET-ASSETS> 384663
<DIVIDEND-INCOME> 6120
<INTEREST-INCOME> 805
<OTHER-INCOME> 0
<EXPENSES-NET> (1852)
<NET-INVESTMENT-INCOME> 5073
<REALIZED-GAINS-CURRENT> 4030
<APPREC-INCREASE-CURRENT> 21723
<NET-CHANGE-FROM-OPS> 30826
<EQUALIZATION> 356132
<DISTRIBUTIONS-OF-INCOME> (1960)
<DISTRIBUTIONS-OF-GAINS> (335)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 497195
<NUMBER-OF-SHARES-REDEEMED> (143356)
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 384663
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 1499
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 2398
<AVERAGE-NET-ASSETS> 308170
<PER-SHARE-NAV-BEGIN> 10.00
<PER-SHARE-NII> .14
<PER-SHARE-GAIN-APPREC> .61
<PER-SHARE-DIVIDEND> (.05)
<PER-SHARE-DISTRIBUTIONS> (.01)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.69
<EXPENSE-RATIO> .63
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
REPORT OF INDEPENDENT ACCOUNTANTS
To the Board of Directors of
The SEI Institutional Investments Trust:
In planning and performing our audit of the financial statements and financial
highlights of the SEI Institutional Investments Trust consisting of the Large
Cap Fund, Small Cap Fund, Core Fixed Income Fund and the International Equity
Fund (collectively, the "Trust") for the year ended May 31, 1997, we
considered its internal control structure, including procedures for
safeguarding securities, in order to determine our auditing procedures for
the purpose of expressing our opinion on the financial statements and
financial highlights and to comply with the requirements of Form N-SAR, not
to provide assurance on the internal control structure.
The management of the Trust is responsible for establishing and maintaining
an internal control structure. In fulfilling this responsibility, estimates
and judgments by management are required to assess the expected benefits and
related costs of internal control structure policies and procedures. Two of
the objectives of an internal control structure are to provide management with
reasonable, but not absolute, assurance that assets are safeguarded against
loss from unauthorized use or disposition and that transactions are executed in
accordance with management's authorization and recorded properly to permit
preparation of financial statements in conformity with generally accepted
accounting principles.
Because of inherent limitations in any internal control structure, errors or
irregularities may occur and not be detected. Also, projection of any
evaluation of the structure 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 the internal control structure would not necessarily
disclose all matters in the internal control structure 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 the specific internal control structure elements do not reduce
to a relatively low level the risk that errors or irregularities in amounts
that would be material in relation to the financial statements and financial
highlights 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 internal control structure,
including procedures for safeguarding securities, that we consider to be
material weaknesses, as defined above, as of May 31, 1997.
This report is intended solely for the information and use of management and
Board of Directors of the SEI Institutional Investments Trust and the
Securities and Exchange Commission.
2400 Eleven Penn Center
Philadelphia, Pennsylvania
July 15 , 1997
