<PAGE>
Allmerica Investment Trust (the "Trust")
Supplement effective July 1, 1999
to
Statement of Additional Information ("SAI")
dated May 1, 1999
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The last sentence of the first paragraph under the heading "Select Emerging
Markets Fund" in the section entitled, "DESCRIPTION OF THE FUNDS AND THEIR
INVESTMENTS AND RISKS", on page 3 of the SAI is amended to read as follows:
A company is considered as primarily doing business in a developing country
if (i) the company derives at least 50% of its gross revenues or profits
from either goods or services produced or sold in the developing country or
(ii) at least 50% of the company's assets are situated in the developing
country.
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The second sentence of the first paragraph under the heading "High Yield
Securities" in the section entitled, "Investment Strategies and Techniques", on
page 21 of the SAI is amended to read as follows:
The Select Growth Fund and the Select Growth and Income Fund may not invest
more than 15% of their assets, the Select Income Fund and the Select
Capital Appreciation Fund may not invest more than 25% of their assets and
the Select Emerging Markets Fund may not invest more than 35% of its assets
at the time of investment in securities rated below Baa by Moody's or BBB
by S&P, or equivalently rated by another NRSRO, or unrated but believed by
the Sub-Adviser to be of comparable quality.
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The chart containing information about the Trustees and Officers of the
Trust under the section entitled, "MANAGEMENT OF THE TRUST", on page 25 of the
SAI is amended to delete the information relative to David J. Mueller and to
include the following information:
<TABLE>
<CAPTION>
Positions Held Present Position and Principal
Name, Address and Age with the Trust(1) Occupations During the Past Five Years
- -------------------------- ------------------------- --------------------------------------------
<S> <C> <C>
Paul T. Kane (42) Assistant Vice President Assistant Vice President, First Allmerica
440 Lincoln Street and Treasurer since June 1999; Vice President/Treasurer
Worcester, Massachusetts (Principal Accounting of Tax & Financial Services, BISYS Fund
Officer) Services, 1997-1999; Director of Shareholder
Reporting, Fidelity Investments, 1992-1997
</TABLE>
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The chart listing the persons who are affiliated with the Trust and the
Manager under the section entitled, "INVESTMENT MANAGEMENT AND OTHER SERVICES",
on page 29 of the SAI is amended to delete the information relative to David J.
Mueller and to include the following:
<PAGE>
<TABLE>
<CAPTION>
Position(s) held Position(s) held with the Manager
Name with the Trust or Sub-Adviser of the Trust
- ---- -------------- ---------------------------
<S> <C> <C>
Paul T. Kane Assistant Vice President and Treasurer Assistant Vice President, AFIMS
(Principal Accounting Officer)
</TABLE>
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The chart listing the persons who are affiliated with the Trust and
Allmerica Investments, Inc. under the section entitled, "Underwriter", on page
38 of the SAI is amended to delete the information relating to David J. Mueller
and to include the following:
<TABLE>
<CAPTION>
Position(s) held Position(s) held
Name with the Trust with AII
- ---- -------------- --------
<S> <C> <C>
Paul T. Kane Assistant Vice President and Treasurer Assistant Vice President
(Principal Accounting Officer)
</TABLE>
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Effective as of the date hereof, the name of the Sub-Adviser of the Select
Emerging Markets Fund has been changed from Schroder Capital Management
International Inc. to Schroder Investment Management North America Inc.
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The first sentence in the fifth paragraph on page 28 of the SAI under the
section entitled, "INVESTMENT MANAGEMENT AND OTHER SERVICES", is amended to read
as follows:
AFIMS, First Allmerica and Allmerica Financial Life are direct or indirect
wholly-owned subsidiaries of AFC, a publicly-traded Delaware holding
company for a group of affiliated companies, the largest of which is First
Allmerica.
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The second sentence in the fifth full paragraph on page 29 of the SAI under the
section entitled, "INVESTMENT MANAGEMENT AND OTHER SERVICES", is amended to read
as follows:
AAM is a direct, wholly-owned subsidiary of AFC.
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The following sentence is added after the first sentence under the heading,
"Underwriter", in the section entitled, "Service Agreements", on page 38 of the
SAI:
AII is an indirect, wholly-owned subsidiary of AFC.
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