Merrill Corp - Ameriprise Financial [MCS] Columbia Acorn Trust Multi-Class Semi-Annual Report [Funds] 0...ED [AUX] | cmashak | 24-Aug-12 17:28 | 12-14557-2.aa | Sequence: 1 CHKSUM Content: 62817 Layout: 60096 Graphics: 56065 CLEAN Q2 2012 Columbia Acorn Family of Funds Class A, B, C, I, R and R5 Shares Managed by Columbia Wanger Asset Management, LLC Semiannual Report June 30, 2012 n Columbia Acorn® Fund n Columbia Acorn International® n Columbia Acorn USA® n Columbia Acorn International SelectSM n Columbia Acorn SelectSM n Columbia Thermostat FundSM n Columbia Acorn Emerging Markets FundSM n Columbia Acorn European FundSM Not FDIC insured • No bank guarantee • May lose value JOB: 12-14557-2 CYCLE#;BL#: 4; 0 TRIM: 8.25" x 10.75" COMPOSITE COLORS: Black, PANTONE 208 U, ~HTML color, ~HTML color 2, ~note-color 2 GRAPHICS: Acorn Z cvr k crop.eps, col_mgmt_R_bold_KO_new.eps V1.5 Merrill Corp - Ameriprise Financial [MCS] Columbia Acorn Trust Multi-Class Semi-Annual Report [Funds] 0...ED [AUX] | cmashak | 24-Aug-12 17:28 | 12-14557-2.aa | Sequence: 2 CHKSUM Content: 23529 Layout: 2229 Graphics: No Graphics CLEAN The views expressed in the “Chattering Squirrels” and “In a Nutshell” commentaries reflect the current views of the respective authors. These views are not guarantees of future performance and involve certain risks, uncertainties and assumptions that are difficult to predict so actual outcomes and results may differ significantly from the views expressed. These views are subject to change at any time based upon economic, market or other conditions and the respective authors disclaim any responsibility to update such views. These views may not be relied upon as investment advice and, because investment decisions for a Columbia Acorn Fund are based on numerous factors, may not be relied upon as an indication of trading intent on behalf of any particular Columbia Acorn Fund. References to specific company’s securities should not be construed as a recommendation or investment advice and there can be no assurance that as of the date of publication of this report, the securities mentioned in each Fund’s portfolio are still held or that the securities sold have not been repurchased. Acorn®, Acorn USA® and Acorn International® are service marks owned and registered by Columbia Acorn Trust. ColumbiaSM, Columbia Management®, and the Columbia Management Logo® are service marks owned and/or registered by Ameriprise Financial, Inc. JOB: 12-14557-2 CYCLE#;BL#: 4; 0 TRIM: 8.25" x 10.75" COMPOSITE COLORS: PANTONE 208 U, ~note-color 2 GRAPHICS: none V1.5 Merrill Corp - Ameriprise Financial [MCS] Columbia Acorn Trust Multi-Class Semi-Annual Report [Funds] 0...ED [AUX] | cmashak | 24-Aug-12 17:28 | 12-14557-2.ac | Sequence: 1 CHKSUM Content: 53573 Layout: 44457 Graphics: 51908 CLEAN You are invited to the 2012 Columbia Acorn Funds Shareholder Information Meeting Join us to hear presentations by Columbia Acorn Fund’s lead portfolio manager Chuck McQuaid and other members of the Columbia Wanger Asset Management investment team. Where: Drinker Biddle & Reath LLP N Clinton St N Canal St Merchandise Mart Plz St S Wells W Mart Center Dr N Lasalle St 191 North Wacker Drive, Suite 3700 N Clark St Chicago, IL W Lower Wacker Dr N Milwaukee Ave W Wacker Dr When: Wednesday, September 19, 2012 Pl N Post W Haddock Pl N Jefferson St N Franklin St N Franklin 12 p.m. CST N Clinton St N Lasalle St N Canal St N Clark St W Lake St A buffet lunch will be served beginning at 11:30. S Wells St S Wells N RSVP: 800.922.6769 by September 14, 2012 W Couch Pl W Randolph St W Randolph St Dr Wacker N Lower N Jefferson St N Clinton St N Canal St Webcast Replay: Available at columbiamanagement.com Dr N Wacker N Lasalle St N Franklin St N Franklin N Clark St in October. W Court Pl Public Transportation W Washington St W Washington St For directions using public transportation, call W Calhoun Pl 312.836.7000 or visit the Chicago Transit Authority website at transitchicago.com. Metra information W Madison St W Madison St is also available by calling this number or can be found at metrarail.com. Parking Information Two parking options are located on Lake Street in the same block as the meeting location, which is between N. Wacker Drive and N. Franklin Street. Lake Street runs one way east after crossing N. Wacker Drive. Hourly parking rates apply at both locations. The first, with signage stating “Public Parking” (phone: 312.267.6867), provides direct access to the building in which the meeting will be held. The second option is a “Self Park” garage (phone: 312.201.1795) located next to the first but without direct access to the building. Driving Directions From the south: Take 1-57 to the Dan Ryan Expressway. Follow the signs for the Kennedy Expressway West. Travel on the Kennedy and exit using the Washington exit (Exit 51C). Turn right onto W. Washington. Proceed east on Washington until you reach Canal Street. Turn left on Canal Street. Travel on Canal to Lake Street. Turn right on Lake Street. Take Lake Street across N. Wacker Drive to the southeast corner of Lake Street and N. Wacker Drive. From the north: Take the Kennedy Expressway (I-90/94) south to Chicago. Exit in the city using the W. Randolph Street exit (Exit 51B). Turn right onto W. Randolph Street. Proceed west on Randolph Street until you reach N. Halsted Street. Turn right onto N. Halsted Street. Travel on Halsted to W. Lake Street. Turn right on Lake Street. Take Lake Street across N. Wacker Drive to the southeast corner of Lake Street and N. Wacker Drive. From the west: Take the Eisenhower Expressway (I-290) from the west. Follow the signs for the Kennedy Expressway West. Travel on the Kennedy and exit using the Washington exit (Exit 51C). Turn right onto W. Washington. Proceed east on Washington until you reach Canal Street. Turn left on Canal Street. Travel on Canal to Lake Street. Turn right on Lake Street. Take Lake Street across N. Wacker Drive to the southeast corner of Lake Street and N. Wacker Drive. From the southwest: Wacker Drive Construction Take the Stevenson Expressway (I-55). Exit to the Kennedy Expressway Please keep Chicago’s Wacker Drive (North-Wisconsin). Travel on the Kennedy and exit using the Washington exit construction project in mind when planning (Exit 51C). Turn right onto W. Washington. Proceed east on Washington until your route. Current information on the you reach Canal Street. Turn left on Canal Street. Travel on Canal to Lake project can be found at wackerdrive.org. Street. Turn right on Lake Street. Take Lake Street across N. Wacker Drive to the southeast corner of Lake Street and N. Wacker Drive. JOB: 12-14557-2 CYCLE#;BL#: 4; 0 TRIM: 8.25" x 10.75" COMPOSITE COLORS: Black, PANTONE 208 U, ~note-color 2, ~note-color 3 GRAPHICS: 14557-2 map_large.eps, car_208.eps, park_208.eps, train_208.eps V1.5 Merrill Corp - Ameriprise Financial [MCS] Columbia Acorn Trust Multi-Class Semi-Annual Report [Funds] 0...ED [AUX] | cmashak | 24-Aug-12 17:28 | 12-14557-2.ba | Sequence: 1 CHKSUM Content: 43712 Layout: 60959 Graphics: No Graphics CLEAN Columbia Acorn Family of Funds Table of Contents Share Class Performance 2 Columbia Acorn Select In a Nutshell 20 Fund Performance vs. Benchmarks 3 At a Glance 21 Major Portfolio Changes 69 Descriptions of Indexes 4 Statement of Investments 70 Chattering Squirrels: Columbia Thermostat Columbia Thermostat Fund Fund Turns 10 5 In a Nutshell 22 At a Glance 23 Understanding Your Expenses 9 Statement of Investments 76 Columbia Acorn Fund Columbia Acorn Emerging Markets Fund In a Nutshell 12 In a Nutshell 24 At a Glance 13 At a Glance 25 Major Portfolio Changes 28 Major Portfolio Changes 77 Statement of Investments 30 Statement of Investments 79 Columbia Acorn International Portfolio Diversification 83 In a Nutshell 14 Columbia Acorn European Fund At a Glance 15 In a Nutshell 26 Major Portfolio Changes 43 At a Glance 27 Statement of Investments 45 Major Portfolio Changes 84 Portfolio Diversification 54 Statement of Investments 85 Columbia Acorn USA Portfolio Diversification 89 In a Nutshell 16 Columbia Acorn Family of Funds At a Glance 17 Statements of Assets and Liabilities 90 Major Portfolio Changes 55 Statements of Operations 92 Statement of Investments 56 Statements of Changes in Net Assets 94 Columbia Acorn International Select Financial Highlights 100 In a Nutshell 18 Notes to Financial Statements 116 At a Glance 19 Board Approval of the Advisory Agreement 126 Major Portfolio Changes 63 Columbia Acorn Family of Funds Information 130 Statement of Investments 64 Portfolio Diversification 68 JOB: 12-14557-2 CYCLE#;BL#: 4; 0 TRIM: 8.25" x 10.75" COMPOSITE COLORS: Black, PANTONE 208 U, ~note-color 2 GRAPHICS: none V1.5 Merrill Corp - Ameriprise Financial [MCS] Columbia Acorn Trust Multi-Class Semi-Annual Report [Funds] 0...ED [AUX] | cmashak | 24-Aug-12 17:28 | 12-14557-2.ba | Sequence: 2 CHKSUM Content: 17928 Layout: 8848 Graphics: No Graphics CLEAN Columbia Acorn Family of Funds 2012 Mid-year Distributions The following table lists the mid-year distributions for the Columbia Acorn Funds. The record date was June 5, 2012, and the ex-divi- dend date and the payable date was June 6, 2012. Share classes that are not listed did not have any distributions at mid-year. Short-term Long-term Capital Capital Ordinary Reinvestment Gains Gains Income Price Columbia Acorn Fund Class A None $0.35688 None $28.07 Columbia Acorn Fund Class B None $0.35688 None $25.76 Columbia Acorn Fund Class C None $0.35688 None $25.37 Columbia Acorn Fund Class I None $0.35688 None