COLUMBIA ACORN TRUST

                         Supplement dated May 1, 2004
                      To Prospectuses Dated May 1, 2004 of
                               Columbia Acorn Fund
                          Columbia Acorn International
                               Columbia Acorn USA
                              Columbia Acorn Select
                       Columbia Acorn International Select
                            Columbia Thermostat Fund

Effective immediately, the following section entitled "Legal Proceedings" is
added to the Funds' Prospectus:

LEGAL PROCEEDINGS. The Securities and Exchange Commission ("SEC"), the New York
Attorney General ("NYAG") and various other regulatory authorities are
investigating late trading and market timing in mutual fund shares, and have
sent information requests and subpoenas to certain affiliates of Columbia
Management Group, Inc. (collectively, "Columbia"). These affiliates include
Columbia Funds Distributor, Inc. ("CFDI"), the distributor of the Funds' shares,
Columbia Wanger Asset Management, L.P. ("WAM"), the Funds' adviser, and Columbia
Management Advisors, Inc. ("CMA"). CMA is the adviser to the Columbia Family of
Funds but not to the Columbia Acorn Family of Funds. Columbia has not uncovered
any instances where any of its affiliates were knowingly involved in late
trading of mutual fund shares.

     On February 24, 2004, the SEC filed a civil complaint in the United States
District Court for the District of Massachusetts against CFDI and CMA, alleging
that they had violated certain provisions of the federal securities laws in
connection with trading activity in mutual fund shares. Also on February 24,
2004, the NYAG filed a civil complaint in New York Supreme Court, County of New
York against CFDI and CMA alleging that CFDI and CMA had violated certain New
York anti-fraud statutes. Both complaints are based on arrangements between 1998
and 2003 with nine investors for the trading of mutual fund shares. Neither
complaint was filed against WAM nor the Columbia Acorn Family of Funds. However,
the complaints against CFDI and CMA identified Columbia Acorn Fund, Columbia
Acorn International and Columbia Acorn International Select as funds in which
one or more of the nine investors invested. If either CFDI or CMA were
unsuccessful in its defense of those proceedings, it could be barred from
serving as a distributor or investment adviser for any investment company
registered under the Investment Company Act of 1940, as amended (a "registered
investment company"), which could prevent CFDI from serving as the Funds'
distributor and could affect the ability of an affiliated person of CFDI or CMA
to serve as a distributor or investment adviser for any registered investment
company. The Funds have been informed by CFDI that, in such a situation, it will
seek exemptive relief from the SEC to permit it to continue to serve as the
Funds' distributor. There is no assurance that such exemptive relief would be
granted.

On March 15, 2004, CFDI and CMA entered into agreements in principle with the
SEC Division of Enforcement and NYAG in settlement of the charges. Under the
agreements, CFDI and CMA agreed, among other things, to the following
conditions: payment of $70 million in disgorgement; payment of $70 million in
civil penalties; an order requiring CFDI and CMA to cease and desist from
violations of the antifraud provisions and other provisions of the federal
securities laws; governance changes designed to maintain the independence of the
mutual fund boards of trustees and ensure compliance with securities laws and
fiduciary duties; and retention of an independent consultant to review CFDI's
and CMA's compliance policies and procedures. The agreement requires the final
approval of the SEC. In a separate agreement with the NYAG, Columbia has agreed
to reduce mutual fund fees by $80 million over a five-year period.

As a result of these matters or any adverse publicity or other developments
resulting from them, there may be increased redemptions or reduced sales of Fund
shares, which could increase transaction costs or operating expenses, or have
other adverse consequences for the Funds.



                      COLUMBIA ACORN INTERNATIONAL SELECT

                         Supplement dated May 1, 2004
    to Prospectus dated May 1, 2004 of Columbia Acorn International Select

   Through July 1, 2004, the fourth paragraph under the heading "Principal
Investment Strategies" on page 2 is deleted in its entirety and replaced by the
following paragraph:

   "Columbia Acorn International Select is an international fund and, under
normal circumstances, invests at least 80% of its net assets (plus any
borrowings for investment purposes) in the stocks of foreign companies based in
developed markets outside the U.S."