<PAGE>
SEI INSTITUTIONAL MANAGED TRUST
SMALL CAP VALUE FUND
HIGH YIELD BOND FUND
SUPPLEMENT DATED SEPTEMBER 15, 1999 TO THE
CLASS A PROSPECTUSES DATED JANUARY 31, 1999
THIS SUPPLEMENT PROVIDES NEW AND ADDITIONAL INFORMATION BEYOND THAT CONTAINED IN
THE CLASS A PROSPECTUSES, AND SHOULD BE READ IN CONJUNCTION WITH SUCH
PROSPECTUSES.
The Board of Trustees of SEI Institutional Managed Trust (the "Trust"),
including all of the Trustees who are not "interested persons" of the Trust,
have appointed Security Capital Global Capital Management Group Incorporated
("Security Capital"), as an additional Sub-Adviser to the Trust's Small Cap
Value Fund (the "Fund"). Security Capital was approved as a Sub-Adviser at the
Quarterly Meeting of the Board of Trustees held on September 13-14, 1999, and
its appointment does not require Shareholder approval. This procedure for adding
or replacing Sub-Advisers was approved by the Trust's Shareholders on November
13, 1995, and was authorized by an exemptive order issued to the Trust by the
Securities and Exchange Commission on April 29, 1996.
In evaluating Security Capital, the Trustees received written and oral
information from both SEI Investments Management Corporation ("SIMC") and
Security Capital. SIMC recommended the selection of Security Capital and
reviewed the considerations and search process that led to its recommendation.
The Trustees also met with representatives of Security Capital and considered
information about portfolio managers, investment philosophy, strategies and
process, as well as other factors. In appointing Security Capital, the Trustees
carefully evaluated: (1) the nature and quality of the services expected to be
rendered to the Fund by Security Capital; (2) the distinct investment objective
and policies of the Fund; (3) the history, reputation, qualification and
background of Security Capital's personnel and its financial condition; (4) its
performance track record; and (5) other factors deemed relevant. The Trustees
also reviewed the fees to be paid to Security Capital, including any benefits to
be received by Security Capital or its affiliates in connection with soft dollar
arrangements.
Under the Investment Sub-Advisory Agreement ("Sub-Advisory Agreement") between
SIMC (the "Adviser") and Security Capital relating to the Fund, Security Capital
makes investment decisions for the assets of the Fund allocated to it by SIMC,
and continuously reviews, supervises and administers the Fund's investment
program with respect to these assets. Security Capital is independent of SIMC
and discharges its responsibilities subject to the supervision of SIMC and the
Trustees of the Trust, and in a manner consistent with the Fund's investment
objective, policies and limitations. The Sub-Advisory Agreement is substantially
similar to those in existence between the Adviser and the Trust's other
Sub-Advisers. Specifically, the duties to be performed, standard of care and
termination provisions of the Agreement are similar to the other Agreements. The
Sub-Advisory Agreement will remain in effect until September 2001 (unless
earlier terminated), and will have to be approved annually thereafter by a
majority of the Trustees, including a majority of the Trustees who are not
"interested persons" of the Trust (as defined in the Investment Company Act of
1940).
In connection with the appointment of Security Capital as Sub-Adviser to the
Fund, the "Sub-Advisers" Section on page 22 of the Class A Prospectus containing
the Small Cap Value Fund is amended by inserting the following disclosure
relating to Security Capital:
SECURITY CAPITAL GLOBAL CAPITAL MANAGEMENT GROUP, INCORPORATED: Anthony R.
Manno, Jr., Kenneth D. Statz, and Kevin W. Bedell comprise the Portfolio
Management Committee of Security Capital Global Capital Management Group,
Incorporated ("Security Capital"). The Portfolio Management Committee is
responsible for determining the portfolio composition for the portion of the
Fund's assets allocated to Security Capital. The members of the Portfolio
Management Committee have an average of 18 years of investment experience.
Security Capital was founded in 1995, and is controlled by Security Capital
Investment Research Incorporated. As of August 31, 1999, Security Capital had
approximately $1.3 billion in assets under management, primarily in real estate
and related disciplines.
<PAGE>
Listed below are the names and principal occupations of the principal executive
officers and directors of Security Capital. The principal business address of
the principal executive officers and directors, as it relates to their positions
at Security Capital, is 11 South LaSalle Street, Chicago, Illinois 60603.
<TABLE>
<CAPTION>
- -----------------------------------------------------------------
NAME TITLE
<S> <C>
- -----------------------------------------------------------------
President, Chief Investment Officer
Anthony R. Manno, Jr. & Director
- -----------------------------------------------------------------
Kenneth D. Statz Managing Director
- -----------------------------------------------------------------
Daniel F. Miranda Managing Director
- -----------------------------------------------------------------
Jeffery A. Jacobson Managing Director
- -----------------------------------------------------------------
W. Joseph Houlihan Managing Director
- -----------------------------------------------------------------
Kevin W. Bedell Senior Vice President
- -----------------------------------------------------------------
Alexander K. Daggett Vice President
- -----------------------------------------------------------------
Jeffery C. Nellessen Vice President
- -----------------------------------------------------------------
David T. Novick Chief Compliance Officer
<CAPTION>
- -----------------------------------------------------------------
</TABLE>
The Adviser will pay Security Capital a fee based on a percentage of the average
monthly market value of the assets of the Fund assigned to Security Capital.
--------------------------
At the same Meeting, the Trustees appointed Nomura Corporate Research and Asset
Management Inc. ("Nomura"), as an additional Sub-Adviser to the Trust's High
Yield Bond Fund (the "Fund"). Nomura's appointment does not require Shareholder
approval. This procedure for adding or replacing Sub-Advisers was approved by
the Trust's Shareholders on July 10, 1995, and was authorized by an exemptive
order issued to the Trust by the Securities and Exchange Commission on April 29,
1996.
In evaluating Nomura, the Trustees received written and oral information from
both SEI Investments Management Corporation ("SIMC") and Nomura. SIMC
recommended the selection of Nomura and reviewed the considerations and search
process that led to its recommendation. The Trustees also met with
representatives of Nomura and considered information about portfolio managers,
investment philosophy, strategies and process, as well as other factors. In
appointing Nomura, the Trustees carefully evaluated: (1) the nature and quality
of the services expected to be rendered to the Fund by Nomura; (2) the distinct
investment objective and policies of the Fund; (3) the history, reputation,
qualification and background of Nomura's personnel and its financial condition;
(4) its performance track record; and (5) other factors deemed relevant. The
Trustees also reviewed the fees to be paid to Nomura, including any benefits to
be received by Nomura or its affiliates in connection with soft dollar
arrangements.
Under the Investment Sub-Advisory Agreement ("Sub-Advisory Agreement") between
SIMC (the "Adviser") and Nomura relating to the Fund, Nomura makes investment
decisions for the assets of the Fund allocated to it by SIMC, and continuously
reviews, supervises and administers the Fund's investment program with respect
to these assets. Nomura is independent of SIMC and discharges its
responsibilities subject to the supervision of SIMC and the Trustees of the
Trust, and in a manner consistent with the Fund's investment objective, policies
and limitations. The Sub-Advisory Agreement is substantially similar to those in
existence between the Adviser and the Trust's other Sub-Advisers. Specifically,
the duties to be performed, standard of care and termination provisions of the
Agreement are similar to the other Agreements. The Sub-Advisory Agreement will
remain in effect until September 2001 (unless earlier terminated), and will have
to be approved annually thereafter by a majority of the Trustees, including a
majority of the Trustees who are not "interested persons" of the Trust (as
defined in the Investment Company Act of 1940).
In connection with the appointment of Nomura as Sub-Adviser to the Fund, the
"Sub-Advisers" Section on page 6 of the Class A Prospectus containing the High
Yield Bond Fund is amended by inserting the following disclosure relating to
Nomura:
NOMURA CORPORATE RESEARCH AND ASSET MANAGEMENT INC.: Robert Levine, CFA,
President and Chief Executive Officer of Nomura Corporate Research and Asset
Management Inc. ("Nomura"), and Richard A. Buch, Managing Director and Senior
Portfolio Manager of Nomura, are responsible for managing Nomura's high yield
bond portfolios and for overseeing their high yield bond research and analysis.
Prior to joining Nomura, Mr. Levine was President of Kidder, Peabody High Yield
Asset Management, Inc. and Managing Director of Kidder, Peabody & Co., where he
created their first high yield bond mutual fund. Prior to joining Nomura, Mr.
Buch was with Kidder, Peabody & Co., where he served as Senior Vice President of
the Kidder, Peabody Asset Management, Inc. Mr. Levine and Mr. Buch each have
over 20 years of investment experience.
Nomura was founded in 1991, and is controlled by Nomura Holdings America Inc.
and Nomura Securities Co., Ltd. As of August 31, 1999, Nomura had approximately
$2.5 billion in assets under management.
<PAGE>
Listed below are the names and principal occupations of the principal executive
officers and directors of Nomura. The principal business address of the
principal executive officers and directors, as it relates to their positions at
Nomura, is Two World Financial Center, Building B, New York, New York
10281-1198.
<TABLE>
<CAPTION>
<S> <C>
- -----------------------------------------------------------------
<CAPTION>
NAME TITLE
<S> <C>
- -----------------------------------------------------------------
Robert Levine CEO, President & Director
- -----------------------------------------------------------------
Richard A Buch Managing Director & Director
- -----------------------------------------------------------------
Douglas R. Metcalf Director
- -----------------------------------------------------------------
Shigeki Fujitani Director
- -----------------------------------------------------------------
Atsushi Yoshikawa Co-Chairman of the Board
- -----------------------------------------------------------------
Joeseph R. Schmuckler Co-Chairman of the Board
- -----------------------------------------------------------------
Jennie H. Wong Chief Administrative Officer
<CAPTION>
- -----------------------------------------------------------------
</TABLE>
The Adviser will pay Nomura a fee based on a percentage of the average monthly
market value of the assets of the Fund assigned to Nomura.
--------------------------
Credit Suisse Asset Management, a Sub-Adviser to the High Yield Bond Fund,
recently completed its acquisition of Warburg Pincus Asset Management. The
combined firm will be known as Credit Suisse Asset Management, LLC/Americas. In
connection with this name change, any references in the Prospectus containing
the High Yield Bond Fund to Credit Suisse Asset Management are hereby replaced
with Credit Suisse Asset Management LLC/Americas.
--------------------------
The Prospectuses are hereby amended to reflect these changes.
PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE
