Columbia Acorn Trust

Summary Prospectus

May 1, 2016

Columbia Acorn Family of Funds

Managed by Columbia Wanger Asset Management, LLC

Columbia Acorn USA®

Class		Ticker Symbol
Class A Shares		LAUAX
Class C Shares		LAUCX
Class I Shares		CAUIX
Class R4 Shares		CUSAX
Class R5 Shares		CYSRX
Class Y Shares		CUSYX
Class Z Shares		AUSAX

Before you invest, you may want to review the Fund’s Prospectus, which contains more information about the Fund and its risks. You can find the Fund’s Prospectus, Statement of Additional Information and other information about the Fund online at https://www.columbiathreadneedleus.com/web/columbia/forms-literature/fund-literature. You can also get this information at no cost by calling 800.345.6611 or by sending an email to serviceinquiries@columbiathreadneedle.com. This Summary Prospectus incorporates by reference the Fund’s Prospectus and Statement of Additional Information, both dated May 1, 2016.

As with all mutual funds, the Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.

Investment Objective

Columbia Acorn USA^® (the Fund) seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and members of your immediate family invest, or agree to invest in the future, at least $50,000 in certain classes of shares of eligible funds distributed by Columbia Management Investment Distributors, Inc. (the Distributor). More information about these and other discounts is available from your financial intermediary, and can be found in the Choosing a Share Class section beginning on page 17 of the Fund’s prospectus and in Appendix S to the Statement of Additional Information (SAI) under Sales Charge Waivers beginning on page S-1.

Shareholder Fees (fees paid directly from your investment)
	Class A	Class C	Classes I, R4, R5, Y and Z
Maximum sales charge (load) imposed on purchases (as a % of offering price)	5.75%	None	None
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value)	1.00% ^(a)	1.00% ^(b)	None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
	Class A	Class C	Class I	Class R4	Class R5	Class Y	Class Z
Management fees^(c)	0.89%	0.89%	0.89%	0.89%	0.89%	0.89%	0.89%
Distribution and/or service (12b-1) fees	0.25%	1.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Other expenses^(d)	0.29%	0.23%	0.14%	0.32%	0.19%	0.14%	0.29%
Total annual Fund operating expenses	1.43%	2.12%	1.03%	1.21%	1.08%	1.03%	1.18%

(a)	This charge is imposed on certain investments of between $1 million and $50 million redeemed within 18 months after purchase, as follows: 1.00% if redeemed within 12 months after purchase, and 0.50% if redeemed more than 12, but less than 18, months after purchase, with certain limited exceptions.
(b)	This charge applies to redemptions within 12 months after purchase, with certain limited exceptions.
(c)	Management fees have been restated to reflect current fees based on current asset levels.
(d)	Other expenses have been restated and are based on estimated amounts for the Fund’s current fiscal year, taking into consideration changes in the Fund’s net assets.

Example

The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

■	you invest $10,000 in the applicable class of Fund shares for the periods indicated,
■	your investment has a 5% return each year, and
■	the Fund’s total annual operating expenses remain the same as shown in the Annual Fund Operating Expenses table above.

Although your actual costs may be higher or lower, based on the assumptions listed above, your costs would be:

	1 year	3 years	5 years	10 years
Class A (whether or not shares are redeemed)	$712	$1,001	$1,312	$2,190
Class C (assuming redemption of all shares at the end of the period)	$315	$ 664	$1,139	$2,452
Class C (assuming no redemption of shares)	$215	$ 664	$1,139	$2,452
Class I (whether or not shares are redeemed)	$105	$ 328	$ 569	$1,259
Class R4 (whether or not shares are redeemed)	$123	$ 384	$ 665	$1,466
Class R5 (whether or not shares are redeemed)	$110	$ 343	$ 595	$1,317
Class Y (whether or not shares are redeemed)	$105	$ 328	$ 569	$1,259
Class Z (whether or not shares are redeemed)	$120	$ 375	$ 649	$1,432

1	Columbia Acorn USA®

Portfolio Turnover

The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 35% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (including the amount any borrowings for investment purposes) in U.S. companies.

Under normal circumstances, the Fund (i) invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of initial investment (“Focus Stocks”) and (ii) may also invest in companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of the Fund’s net assets would be invested in Focus Stocks. The Fund may continue to hold, and make additional investments in, Focus Stocks whose market capitalizations have grown to exceed $5 billion, regardless of whether the Fund’s investments in Focus Stocks are a majority of the Fund’s net assets.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Investment Manager), believes that stocks of small- and mid-sized companies, which generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Investment Manager typically seeks companies with:

■	A strong business franchise that offers growth potential.

■	Products and services in which the company has a competitive advantage.

■	A stock price the Investment Manager believes is reasonable relative to the assets and earning power of the company.

The Investment Manager may sell a portfolio holding if the security reaches the Investment Manager's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Investment Manager believes other securities are more attractive. The Investment Manager also may sell a portfolio holding to fund redemptions.

Principal Risks

An investment in the Fund involves risk, including those described below. There is no assurance that the Fund will achieve its investment objective and you may lose money. The value of the Fund’s holdings may decline, and the Fund’s net asset value (NAV) and share price may go down.

Active Management Risk. The Investment Manager’s active management of the Fund could cause the Fund to underperform its benchmark index and/or other funds with similar investment objectives and/or strategies.

Market Risk. Market risk refers to the possibility that the market values of securities or other investments that the Fund holds will fall, sometimes rapidly or unpredictably, or fail to rise. An investment in the Fund could lose money over short or long periods.

Small- and Mid-Cap Company Securities Risk. Investments in small- and mid-capitalization companies (small- and mid-cap companies) often involve greater risks than investments in larger, more established companies (larger companies) because small- and mid-cap companies tend to have less predictable earnings and may lack the management experience, financial resources, product diversification and competitive strengths of larger companies. Securities of small- and mid-cap companies may be less liquid and more volatile than the securities of larger companies.

Issuer Risk. An issuer in which the Fund invests may perform poorly, and the value of its securities may therefore decline, which would negatively affect the Fund’s performance. Poor performance may be caused by poor management decisions, competitive pressures, breakthroughs in technology, reliance on suppliers, labor problems or shortages, corporate restructurings, fraudulent disclosures, natural disasters or other events, conditions or factors.

Sector Risk. At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic, regulatory, political or market events or conditions, which may make the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly. Generally, the more the Fund diversifies its investments, the more it spreads risk and potentially reduces the risks of loss and volatility.

Columbia Acorn USA®

Performance Information

The following bar chart and table show you how the Fund has performed in the past, and can help you understand the risks of investing in the Fund. The bar chart shows how the Fund’s Class Z share performance has varied for each full calendar year shown. The table below the bar chart compares the Fund’s returns for the periods shown with the Russell 2000 Index. This index measures the performance of the 2,000 smallest companies in the Russell 3000 Index, which represents approximately 10% of the total market capitalization of the Russell 3000 Index.

The performance of one or more share classes shown in the Average Annual Total Returns table below includes the Fund’s Class Z share returns (adjusted to reflect the higher class-related operating expenses of such classes, where applicable) for periods prior to the indicated inception date of such share classes. Except for differences in fees and expenses, all share classes of the Fund would have substantially similar annual returns because all share classes of the Fund invest in the same portfolio of securities.

The after-tax returns shown in the Average Annual Total Returns table below are calculated using the highest historical individual U.S. federal marginal income tax rates and do not reflect the impact of state, local or foreign taxes. Your actual after-tax returns will depend on your personal tax situation and may differ from those shown in the table. In addition, the after-tax returns shown in the table do not apply to shares held in tax-advantaged accounts such as 401(k) plans or Individual Retirement Accounts (IRAs). The after-tax returns are shown only for Class Z shares and will vary for other share classes. Returns after taxes on distributions and sale of Fund shares are higher than before-tax returns for certain periods shown because they reflect the tax benefit of capital losses realized on the redemption of Fund shares.

The Fund’s past performance (before and after taxes) is no guarantee of how the Fund will perform in the future. Updated performance information can be obtained by calling toll-free 800.345.6611 or visiting columbiathreadneedle.com/us.

Year by Year Total Return (%) as of December 31 Each Year*	Best and Worst Quarterly Returns During the Period Shown in the Bar Chart
	_Best	_{3rd Quarter 2009}	_23.55%
	_Worst	_{4th Quarter 2008}	_-27.96%

*	Year to Date return as of March 31, 2016: -6.04%

Average Annual Total Returns After Applicable Sales Charges (for periods ended December 31, 2015)

	Share Class Inception Date	1 Year	5 Years	10 Years
Class Z	09/04/1996
returns before taxes		-1.36%	8.93%	6.17%
returns after taxes on distributions		-7.93%	5.87%	4.49%
returns after taxes on distributions and sale of Fund shares		4.75%	7.14%	5.02%
Class A returns before taxes	10/16/2000	-7.26%	7.37%	5.26%
Class C returns before taxes	10/16/2000	-2.92%	7.89%	5.10%
Class I returns before taxes	09/27/2010	-1.19%	9.08%	6.24%
Class R4 returns before taxes	11/08/2012	-1.36%	8.94%	6.18%
Class R5 returns before taxes	11/08/2012	-1.23%	8.99%	6.20%
Class Y returns before taxes	11/08/2012	-1.23%	9.02%	6.21%
Russell 2000 Index (reflects no deductions for fees, expenses or taxes)		-4.41%	9.19%	6.80%

3	Columbia Acorn USA®

Fund Management

Investment Manager: Columbia Wanger Asset Management, LLC

Portfolio Manager	Title	Role with Fund	Service with the Fund Since
Matthew A. Litfin, CFA	Director of Research (U.S.) and Portfolio Manager	Lead manager since 2016	2015
William J. Doyle, CFA	Portfolio Manager and Analyst	Co-manager since 2014	2006

Purchase and Sale of Fund Shares

You may purchase or redeem shares of the Fund on any business day by contacting the Fund in the ways described below:

Online		Regular Mail		Express Mail		By Telephone
columbiathreadneedle.com/us		Columbia Funds, c/o Columbia Management Investment Services Corp. P.O. Box 8081 Boston, MA 02266-8081		Columbia Funds, c/o Columbia Management Investment Services Corp. 30 Dan Road, Suite 8081 Canton, MA 02021-2809		800.422.3737

You may purchase shares and receive redemption proceeds by electronic funds transfer, by check or by wire. If you maintain your account with a broker-dealer or other financial intermediary, you must contact that financial intermediary to buy, sell or exchange shares of the Fund through your account with the intermediary.

The minimum initial investment amounts for the share classes offered by the Fund are shown below:

Minimum Initial Investment

Class	Category of eligible account	For accounts other than systematic investment plan accounts	For systematic investment plan accounts
Classes A & C	All accounts other than IRAs	$2,000	$100
Classes A & C	IRAs	$1,000	$100
Classes I, R4 & Y	All eligible accounts	None	N/A
Class R5	Combined underlying accounts of eligible registered investment advisers	$100,000	N/A
Class R5	Omnibus retirement plans	None	N/A
Class Z	All eligible accounts	$0, $1,000 or $2,000 depending upon the category of eligible investor	$100

There is no minimum additional investment for any share class.

Tax Information

The Fund normally distributes net investment income and net realized capital gains, if any, to shareholders. These distributions are generally taxable to you as ordinary income, qualified dividend income or capital gains, unless you are investing through a tax-advantaged account, such as a 401(k) plan or an IRA. If you are investing through a tax-advantaged account, you may be taxed upon withdrawals from that account.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and its related companies – including the Investment Manager, the Distributor and Columbia Management Investment Services Corp. (the Transfer Agent) – may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your financial advisor to recommend the Fund over another investment. These potential conflicts of interest may be heightened with respect to broker-dealers owned by Ameriprise Financial and/or its affiliates. Ask your financial advisor or visit your financial intermediary's website for more information.

Columbia Acorn USA®

Columbia Acorn Family of Funds

Columbia Threadneedle Investments is the global brand name of the Columbia and Threadneedle group of companies.

columbiathreadneedle.com/us

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