<PAGE>
Allmerica Investment Trust (the "Trust")
Supplement effective September 1, 1999
to
Statement of Additional Information ("SAI")
dated May 1, 1999
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The following is added at the end of the first paragraph under the heading
"Select Income Fund" in the section entitled, "DESCRIPTION OF THE FUNDS AND
THEIR INVESTMENTS AND RISKS", on page 7 of the SAI:
The Fund may also invest in interest-only and principal-only Treasury
securities and in municipal bonds when such bonds are deemed by the
Sub-Adviser to be attractive investments for the portfolio. The Fund serves
as an investment vehicle for variable annuity contracts and variable life
insurance policies. Investments by the Fund in municipal bonds offer no tax
benefits in addition to those already offered to variable annuity contract
owners and variable life insurance policyholders.
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The following is added on page 24 of the SAI after the section entitled,
"Stripped Mortgage-Backed Securities", under the heading, "Investment Strategies
and Techniques":
Interest-only and Principal-only Treasury Securities
The Select Income Fund and Government Bond Fund may invest in
separately-traded principal and interest components of U.S. Treasury
securities. Treasury securities are high-quality securities issued or
guaranteed by the U.S. Government and backed by the full faith and credit
of the U.S. Treasury. Treasury securities include Treasury bills, notes and
bonds, which may differ only in their interest rates, maturities and times
of issuance. The yield to maturity on an interest-only Treasury security is
extremely sensitive to the rate of principal payments, and a rapid rate of
principal payments may have a material, adverse effect on the portfolio's
yield to maturity from these securities. The market value of principal-only
Treasury securities is unusually volatile in response to changes in
interest rates.
Municipal Securities
The Select Income Fund may invest in municipal bonds. Municipal securities
are debt obligations issued by or on behalf of states, cities,
municipalities and other public authorities. The two principal
classifications of municipal securities are "general obligation" securities
and "revenue" securities. General obligation securities are secured by the
issuer's pledge of its full faith, credit and taxing power for the payment
of principal and interest. Revenue securities are payable only from the
revenues derived from a particular facility or class of facilities or, in
some cases, from the proceeds of a special excise tax or other specific
revenue source such as the user of a facility being financed. Revenue
securities may include private activity bonds. Such bonds may be issued by
or on behalf of public authorities to finance various privately operated
facilities
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and are not payable from the unrestricted revenues of the issuer. As a
result, the credit quality of private activity bonds is frequently related
directly to the credit standing of private corporations or other entities.
In addition, the interest on private activity bonds issued after August 7,
1986 is subject to the federal alternative minimum tax.
Municipal securities can be significantly affected by political changes as
well as uncertainties in the municipal market related to taxation,
legislative changes, or the rights of municipal security holders. Because
many municipal securities are issued to finance similar projects,
especially those relating to education, health care, transportation and
utilities, conditions in those sectors can affect the overall municipal
market. In addition, changes in the financial condition of an individual
municipal issuer can affect the overall municipal market.
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Footnote (1) under the section entitled, "INVESTMENT MANAGEMENT AND
OTHER SERVICES", on page 31 of the SAI is amended to change the management
fees for the Select Aggressive Growth Fund and Select Capital Appreciation
Fund as follows:
(1) The Manager's fees for the Select Aggressive Growth Fund, Select Capital
Appreciation Fund, Select International Equity Fund, Growth Fund and Select
Growth and Income Fund, computed daily at an annual rate based on the
average daily net assets of each Fund, are based on the following schedule:
<TABLE>
<CAPTION>
Select Select Growth
Select Aggressive Select Capital International and Income
Assets Growth Fund Appreciation Fund Equity Fund Growth Fund Fund
------- ----------- ----------------- ----------- ----------- ----
<S> <C> <C> <C> <C> <C>
First $100 Million........ 1.00% 1.00% 1.00% 0.60% 0.75%
Next $150 Million......... 0.90% 0.90% 0.90% 0.60% 0.70%
Next $250 Million......... 0.80% 0.80% 0.85% 0.40% 0.65%
Next $500 Million......... 0.70% 0.70% 0.85% 0.35% 0.65%
Over $1 Billion........... 0.65% 0.65% 0.85% 0.35% 0.65%
</TABLE>
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Footnote (6) under the section entitled, "INVESTMENT MANAGEMENT AND OTHER
SERVICES", on page 32 of the SAI is amended to change the Sub-Adviser fee for
the Select Aggressive Growth Fund as follows:
(6) For its services, NACM will receive a fee computed daily at an annual rate
based on the average daily net assets of the Select Aggressive Growth Fund,
under the following schedule:
Assets Rate
------ ----
First $100 Million.......................... 0.60%
Next $150 Million........................... 0.50%
Next $250 Million........................... 0.40%
Next $250 Million........................... 0.375%
Over $750 Million........................... 0.35%
2
