Columbia Acorn Trust

                        Supplement dated January 16, 2004
                      to Prospectuses dated May 1, 2003 of
                               Columbia Acorn Fund
                          Columbia Acorn International
                               Columbia Acorn USA
                              Columbia Acorn Select
                       Columbia Acorn International Select
                            Columbia Thermostat Fund

Legal Proceedings Involving Affiliates

The Securities and Exchange Commission (the "SEC"), the New York Attorney
General 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. ("CMG")
(collectively, "Columbia"). These affiliates include Columbia Funds Distributor,
Inc. ("CFDI"), the distributor of the Funds' shares, and Columbia Management
Advisors, Inc. ("CMA"). CMA is the adviser to the Columbia Family of Funds BUT
IS NOT THE ADVISER TO THE COLUMBIA ACORN FAMILY OF FUNDS. Columbia has not
uncovered any instances where Columbia entities were knowingly involved in late
trading of mutual fund shares. Columbia has identified a limited number of
investors who had informal arrangements for trading shares of various funds
managed by subsidiaries of CMG between 1998 and 2003. A majority of the
transactions in connection with these arrangements occurred in one international
fund and two domestic funds in the Columbia Family of Funds. The majority of the
trading under these arrangements was made by three entities. A substantial
majority of the trading had ended by October 2002. None of these arrangements
exists today. Information relating to those trading arrangements has been
supplied to various regulatory authorities. The Fund's adviser, Columbia Wanger
Asset Management, L.P. ("WAM") is a wholly owned subsidiary of CMG.

The SEC staff has issued notices to the effect that it has made a preliminary
determination to recommend that the SEC bring civil enforcement actions,
including injunctive proceedings against CFDI and CMA, alleging that they have
violated certain provisions of the federal securities laws. Columbia believes
that those allegations are based principally on the trading arrangements
referred to above. WAM HAS NOT BEEN NAMED IN THESE NOTICES. CFDI and CMA are
engaged in discussions with the SEC staff in an effort to reach a satisfactory
resolution of these matters. However, there can be no assurance that such a
resolution will be reached. Any potential resolution of these matters may
include, but not be limited to, sanctions, financial penalties, damages or
injunctions regarding CFDI or CMA, and structural changes in the conduct of
their business.

Although Columbia does not believe that these regulatory developments or their
resolution will have a material adverse effect on the Funds, or on the ability
of CFDI or WAM to provide services to the Funds, there can be no assurance that
these matters or any publicity relating to these matters or other developments
resulting from them will not adversely effect sales or redemptions of Fund
shares or otherwise effect the Funds.