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</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000804239
<NAME> SEI INSTITUTIONAL MANAGED TRUST
<SERIES>
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<NAME> SMALL CAP GROWTH - CLASS A
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<TABLE> <S> <C>
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<CIK> 0000804239
<NAME> SEI INSTITUTIONAL MANAGED TRUST
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<NAME> SMALL CAP GROWTH - CLASS D
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</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000804239
<NAME> SEI INSTITUTIONAL MANAGED TRUST
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<NAME> MID-CAP
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<ACCUM-APPREC-OR-DEPREC> (2227)
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<EXPENSES-NET> (404)
<NET-INVESTMENT-INCOME> 376
<REALIZED-GAINS-CURRENT> 3053
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<DISTRIBUTIONS-OF-INCOME> (344)
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</TABLE>
<TABLE> <S> <C>
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<CIK> 0000804239
<NAME> SEI INSTITUTIONAL MANAGED TRUST
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<NAME> LARGE CAP GROWTH
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</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000804239
<NAME> SEI INSTITUTIONAL MANAGED TRUST
<SERIES>
<NUMBER> 111
<NAME> SMALL CAP VALUE
<MULTIPLIER> 1,000
<S> <C>
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<OVERDISTRIBUTION-NII> 0
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<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> (16041)
<NET-ASSETS> 430010
<DIVIDEND-INCOME> 4321
<INTEREST-INCOME> 1698
<OTHER-INCOME> 0
<EXPENSES-NET> (4590)
<NET-INVESTMENT-INCOME> 1429
<REALIZED-GAINS-CURRENT> 6703
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<DISTRIBUTIONS-OF-INCOME> (1046)
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<NUMBER-OF-SHARES-SOLD> 39431
<NUMBER-OF-SHARES-REDEEMED> (207956)
<SHARES-REINVESTED> 31295
<NET-CHANGE-IN-ASSETS> 106673
<ACCUMULATED-NII-PRIOR> 807
<ACCUMULATED-GAINS-PRIOR> 35962
<OVERDISTRIB-NII-PRIOR> 0
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<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 4590
<AVERAGE-NET-ASSETS> 424736
<PER-SHARE-NAV-BEGIN> 17.85
<PER-SHARE-NII> .05
<PER-SHARE-GAIN-APPREC> (2.22)
<PER-SHARE-DIVIDEND> (.04)
<PER-SHARE-DISTRIBUTIONS> (1.97)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 13.67
<EXPENSE-RATIO> 1.10
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000804239
<NAME> SEI INSTITUTIONAL MANAGED TRUST
<SERIES>
<NUMBER> 121
<NAME> HIGH YIELD BOND
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> YEAR
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<INVESTMENTS-AT-COST> 309825
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<EXPENSES-NET> (2284)
<NET-INVESTMENT-INCOME> 24014
<REALIZED-GAINS-CURRENT> 3851
<APPREC-INCREASE-CURRENT> (25378)
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<NUMBER-OF-SHARES-SOLD> 194775
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</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000804239
<NAME> SEI INSTITUTIONAL MANAGED TRUST
<SERIES>
<NUMBER> 131
<NAME> TAX MANAGED LARGE CAP
<MULTIPLIER> 1,000
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<PER-SHARE-NAV-END> 9.61
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</TABLE>
To the Board of Trustees of
SEI Institutional Managed Trust
In planning and performing our audit of the
financial statements and financial highlights of
Large Cap Value, Large Cap Growth, Tax
Managed Large Cap, Small Cap Value, Small
Cap Growth, Mid-Cap, Capital Appreciation, Equity
Income, Balanced, Core Fixed Income and High
Yield Bond Funds (constituting SEI Institutional
Managed Trust, hereafter referred to as the "Trust")
for the year ended September 30, 1998, 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 financial highlights and to comply
with the requirements of Form N-SAR, not to
provide assurance on internal control.
The management of the Trust 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 and financial highlights 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 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
internal control and its operation, including controls
over safeguarding securities, that we consider to be
material weaknesses as defined above as of
September 30, 1998.
This report is intended solely for the information and
use of management, the Board of Trustees, and the
Securities and Exchange Commission.
November 23,1998
