COLUMBIA ACORN TRUST

Columbia^SM Acorn^® Fund
Columbia^SM Acorn International^®
Columbia^SM Acorn USA^®
Columbia^SM Acorn International Select^SM
Columbia^SM Acorn Select^SM
Columbia^SM Thermostat Fund^SM

(Each a “Fund” and together the “Funds”)

Supplement dated October 26, 2009 to the Prospectuses
and Statement of Additional Information dated May 1, 2009

Banc of America Investment Services, Inc. (“BAI”) has merged with and into Merrill Lynch, Pierce, Fenner & Smith Incorporated (“MLPF&S”). As such, references to BAI in each Fund’s Prospectuses and in the Statement of Additional Information are hereby deleted and, to the extent that the context requires, are replaced with references to MLPF&S.

Shareholders should retain this Supplement for future reference.

INT-47/26101-1009