(Columbia Acorn USA B) | (Columbia Acorn USA)

Investment Objective

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.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees (Columbia Acorn USA)		Class B Shares (Columbia Acorn USA B)
Maximum sales charge (load) imposed on purchases, as a % of offering price
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	[1]	5.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Columbia Acorn USA)		Class B Shares (Columbia Acorn USA B)
Management fees		0.86%
Distribution and/or service (Rule 12b-1) fees		0.75%
Other expenses	[1]	0.49%
Total annual Fund operating expenses		2.10%

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 Class B shares of the Fund 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 table above.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn USA) (USD $)	1 Year	3 Years	5 Years	10 Years
Class B Shares (Columbia Acorn USA B)	713	958	1,329	2,234

Expense Example, No Redemption (Columbia Acorn USA) (USD $)	1 Year	3 Years	5 Years	10 Years
Class B Shares (Columbia Acorn USA B)	213	658	1,129	2,234

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays 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 20% of the average value of its portfolio.

Principal Investment Strategies

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

Under normal circumstances, the Fund 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 investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Investment Manager), believes that stocks of companies with market capitalizations under $5 billion, 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 that give the company 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

• Investment Strategy Risk – The Investment Manager uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Investment Manager in using these strategies may not produce the returns expected by the Investment Manager, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk – Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably, or fail to rise. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods, or fail to increase in value. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Smaller Company Securities Risk – Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those positions, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Sector Risk – At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

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 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 www.columbiamanagement.com.

The bar chart below shows you how the performance of the Fund's Class B shares has varied from year to year.

Year by Year Total Return (%) as of December 31 Each Year

^[1]

Best and Worst Quarterly Returns During this Period

Best:    3rd quarter 2009:    23.15%

Worst:   4th quarter 2008:   -28.08%

Average Annual Total Return as of December 31, 2011

The table compares the Fund's returns for each period with those of 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.

Average Annual Total Returns (Columbia Acorn USA) (Columbia Acorn USA B)	1 Year	5 Years	10 Years
Class B Shares	(10.36%)	(0.45%)	5.25%
Class B Shares returns after taxes on distributions	(10.46%)	(0.77%)	4.95%
Class B Shares returns after taxes on distributions and sale of Fund shares	(6.60%)	(0.37%)	4.59%
Russell 2000 Index (reflects no deductions for fees, expenses or taxes)	(4.18%)	0.15%	5.62%

The after-tax returns shown in the table above 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-deferred accounts such as 401(k) plans or individual retirement accounts (IRAs).

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.

[1] This charge decreases over time. See About Class B Shares - Sales Charges and Commissions for details.

[1] Other expenses have been restated to reflect contractual changes to certain fees paid by the Fund.

[1] Year-to-date return as of March 31, 2012: 16.06%