<PAGE>
Allmerica Investment Trust (the "Trust")
Supplement effective August 11, 2000
to
Prospectus dated May 1, 2000
The chart containing information on the individuals who are primarily
responsible for the day-to-day management of the Select Aggressive Growth Fund
under the heading "Management of the Funds" is amended to delete all of the
information with respect to Lawrence S. Speidell and Mark W. Stuckelman and to
include the following information with respect to David Pavan:
<TABLE>
<CAPTION>
Fund Name and Name and Title of Service with Business Experience
Sub-Adviser Name Portfolio Manager(s) Sub-Adviser for Past Five Years
---------------- -------------------- ----------- -------------------
<S> <C> <C> <C>
Select Aggressive Growth Fund David Pavan, CFA, 1999-Present He joined NACM in
Nicholas-Applegate Capital Portfolio Manager 1999 as a Portfolio
Management, L.P. ("NACM") Manager for the U.S.
Systematic portfolios.
He was a Quantitative
Analyst at Putnam
Investment Management,
Inc. from 1997-1999.
Prior to 1997, he
served as Portfolio
Manager at Genus in
Canada.
</TABLE>
The section relating to the Select Strategic Growth Fund in the same table noted
above is amended to include the following information with respect to Nicholas
J. Capuano who has replaced Charles Larsen:
<TABLE>
<CAPTION>
Fund Name and Name and Title of Service with Business Experience
Sub-Adviser Name Portfolio Manager(s) Sub-Adviser for Past Five Years
---------------- -------------------- ----------- -------------------
<S> <C> <C> <C>
Select Strategic Growth Fund Nicholas J. Capuano 1990 - Present He joined TCW as an Account
TCW Investment Management Managing Director Manager and later served in
Company ("TCW") U.S. Equities Client Relations and in the
Earnings Momentum Group.
He started in the Small Cap
Equities area in 1994.
</TABLE>
The section relating to the Core Equity Fund in the same table noted above is
amended to delete all of the information with respect to Gary G. Schlarbaum,
Robert J. Marcin, James J. Jolinger and Arden C. Armstrong.
The section relating to the Select Growth and Income Fund in the same table
noted above is amended to delete all of the information with respect to James
C. Wiess.
