Institutional Class: LSSIX Retail Class: LCGRX Class N: LSSNX

Loomis Sayles Small Cap Growth Fund

Summary Prospectus at February 1, 2013

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 and other information about the Fund online at www.loomissayles.com/Prospectus. You can also get this information at no cost by calling 800-633-3330 or by sending an e-mail request to FundInformation@loomissayles.com. The Fund’s Prospectus and Statement of Additional Information (“SAI”), each dated February 1, 2013 are incorporated by reference into this Summary Prospectus.

Investment Objective The Fund’s investment objective is long-term capital growth from investments in common stocks or other equity securities. Fund Fees & Expenses The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The Fund does not impose a sales charge, a redemption fee or an exchange fee.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)	Institutional Class	Retail Class	Class N
Management fees	0.75%	0.75%	0.75%
Distribution and/or service (12b-1) fees	0.00%	0.25%	0.00%
Other expenses	0.20%	0.28%	0.10%1
Total annual fund operating expenses	0.95%	1.28%	0.85%
Fee waiver and/or expense reimbursement2	0.00%	0.03%	0.00%
Total annual fund operating expenses after fee waiver and/or expense reimbursement	0.95%	1.25%	0.85%

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Other expenses for Class N shares are based on estimated amounts for the current fiscal year.

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Loomis, Sayles & Company, L.P. (“Loomis Sayles” or the “Adviser”) has given a binding contractual undertaking to the Fund to limit the amount of the Fund’s total annual fund operating expenses to 1.00%, 1.25% and 0.95% of the Fund’s average daily net assets for Institutional Class shares, Retail Class shares and Class N shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2014 and may be terminated before then only with the consent of the Fund’s Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.00%, 1.25% and 0.95% of the Fund’s average daily net assets for Institutional Class shares, Retail Class shares and Class N shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

Example The 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 assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and the Fund’s operating expenses remain the same. The example for the Institutional Class shares and the Class N shares is based on Total Annual Fund Operating Expenses for all periods. The example for Retail Class shares is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

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	1 year	3 years	5 years	10 years
Institutional Class	$97	$303	$525	$1,166
Retail Class	$127	$403	$699	$1,543
Class N	$87	$271	$471	$1,049

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 for you if your 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 its most recently ended fiscal year, the Fund’s portfolio turnover rate was 77% of the average value of its portfolio. Investments, Risks and Performance Principal Investment Strategies The Fund normally will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in the equity securities of “small-cap companies,” including preferred stocks, warrants, securities convertible into common or preferred stocks and other equity-like interests in an entity. Currently, the Fund defines a small-cap company to be one whose market capitalization either falls within the capitalization range of the Russell 2000 Index, an index that tracks stocks of 2,000 of the smallest U.S. companies, or is $3 billion or less at the time of investment. The Fund may invest the rest of its assets in companies of any size, including large-capitalization companies. In deciding which securities to buy and sell, Loomis Sayles typically seeks to identify companies that it believes have distinctive products, technologies, or services; dynamic earnings growth; prospects for high levels of profitability; and solid management. Loomis Sayles typically does not consider current income when making buy/sell decisions. The Fund may invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in other foreign securities, including emerging markets securities. The Fund may also invest in securities issued pursuant to Rule 144A under the Securities Act of 1933 (“Rule 144A securities”). The Fund may engage, for hedging and investment purposes, in foreign currency transactions, options and futures transactions. Principal Risks The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Credit Risk is the risk that the issuer or guarantor of a fixed-income security in which the Fund invests, or the counterparty to a derivatives or other transaction will fail financially or otherwise be unwilling or unable to meet their obligations to the Fund. Currency Risk is the risk that the value of the Fund’s investments will fall as a result of changes in exchange rates. Loomis Sayles may elect not to hedge currency risk or may hedge imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk is the risk that the value of the Fund’s derivative investments such as forward currency contracts, options and futures transactions will fall, for example, because of changes in the value of the underlying reference instruments, pricing difficulties or lack of correlation with the underlying investments. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. There can be no assurance that the Fund’s derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. This risk is greater for forward currency contracts and other over-the-counter traded derivatives. Investing in derivatives gives rise to other risks, such as leverage risk, liquidity risk, credit risk, counterparty risk, interest rate risk and market risk. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used.

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Emerging Markets Risk is the risk that the Fund’s investments may face greater foreign securities risk. Investing in companies traded in emerging securities markets, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk is the risk that the value of a stock may decline for a number of reasons that relate directly to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods and services, or the equity markets generally. Growth stocks are generally more sensitive to market movements than other types of stocks, primarily because their stock prices are based heavily on future expectations. If Loomis Sayles’ assessment of the prospects for a company’s growth is wrong, or if Loomis Sayles’ judgment of how other investors will value the company’s growth is wrong, then the price of the company’s stock may fall or not approach the value that Loomis Sayles has placed on it. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer’s bonds generally take precedence over the claims of those who own preferred stock or common stock. Foreign Securities Risk is the risk that the value of the Fund’s foreign investments will fall as a result of foreign political, social, economic, environmental, credit, informational or currency changes or other issues relating to foreign investing generally. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. The Fund’s investments in foreign securities may be subject to foreign withholding taxes, which would decrease the yield on those securities. Issuer Risk is the risk that the value of securities may decline due to a number of reasons relating to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods and services. Leverage Risk is the risk associated with securities or practices (e.g., borrowing and the use of certain derivatives) and investment in certain types of derivatives that multiply small index, market or asset price movements into larger changes in value. Use of derivative instruments may involve leverage. When a derivative is used as a hedge against an offsetting position that the Fund also holds, any loss generated by the derivative should be substantially offset by gains on the hedged instrument, and vice versa. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. Futures and forward currency contracts are derivatives and may be subject to this type of risk. Liquidity Risk is the risk that the Fund may be unable to find a buyer for its investments when it seeks to sell them or to receive the price it expects. Securities acquired in a private placement, such as Rule 144A securities, generally are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. Therefore, the Fund may be unable to dispose of such securities when it desires to do so, or at the most advantageous time or price. Liquidity issues may also make it difficult to value the Fund’s investments. Management Risk is the risk that Loomis Sayles’ investment techniques will be unsuccessful and cause the Fund to incur losses. Market Risk is the risk that the market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer’s financial condition, as well as overall market and economic conditions. Small-Capitalization Companies Risk is the risk that the Fund’s investments may be subject to more abrupt price movements, limited markets, increased volatility and less liquidity than investments in larger, more established companies, which could adversely affect the value of the portfolio. Risk/Return Bar Chart and Table The following bar chart and table give an indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual returns for the one-year, five-year, ten-year and life-of-fund periods compare to those of a broad measure of market performance. The Fund’s past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at www.loomissayles.com and/or by calling the Fund toll-free at 800-633-3330.

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Total Returns for Institutional Class Shares

The Fund’s best quarter was 25.29%, (second quarter of 2003), and the Fund’s worst quarter was -26.86%, (fourth quarter of 2008). Average Annual Total Returns for the periods ended December 31, 2012

	One Year	Five Years	Ten Years	Life-of-Fund (12/31/96)
Institutional Class
Return Before Taxes	10.29%	3.50%	11.34%	4.80%
Return After Taxes on Distributions	10.29%	3.50%	11.34%	4.58%
Return After Taxes on Distributions and Sale of Fund Shares	6.69%	3.00%	10.19%	4.12%
Retail Class – Return Before Taxes	9.96%	3.22%	11.04%	4.53%
Class N – Return Before Taxes	10.29%	3.50%	11.34%	4.80%
Russell 2000 Growth Index	14.59%	3.49%	9.80%	4.58%

Because the Fund did not have Class N shares outstanding during the periods shown, performance is that of the Institutional Class shares of the Fund. Class N shares would have had substantially similar returns because they would have been invested in the same portfolio of securities as Institutional Class shares and would only differ to the extent the classes did not have the same expenses. The Class N returns may be higher than the returns of Institutional Class shares because Institutional Class shares are subject to higher expenses. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for the Institutional Class of the Fund. After-tax returns for other classes of the Fund will vary. Index performance reflects no deduction for fees, expenses or taxes. Management Investment Adviser Loomis, Sayles & Company, L.P. Portfolio Managers Mark F. Burns, CFA, Vice President of Loomis Sayles, has served as a portfolio manager of the Fund since 2005. John J. Slavik, CFA, Vice President of Loomis Sayles, has served as a portfolio manager of the Fund since 2005.

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Purchase and Sale of Fund Shares The following chart shows the investment minimum for each class of shares of the Fund:

	Minimum Initial Investment	Minimum Subsequent Investment
Institutional Class	$100,000	$50
Retail Class	$2,500	$50
Class N	No Minimum	No Minimum

Class N shares are intended primarily for employer-sponsored retirement plans held in an omnibus fashion and are not available for purchase by individual investors. Class N shares are also available to funds of funds that are distributed by NGAM Distribution L.P. (the “Distributor”). Please see the section “How to Buy Shares” in the Fund’s Statement of Additional Information (“SAI”) for details. The Fund is closed to new investors; however, in its sole discretion, Loomis Sayles may permit an investor in another Loomis Sayles managed fund or product that follows the same investment strategy as the Fund to transfer assets from that fund or product into the Fund. Loomis Sayles may determine to reopen the Fund for investment at any time without notice to shareholders. For more information see the section “How to Purchase Shares” in the Statutory Prospectus. The Fund’s shares are available for purchase (and are redeemable on any business day) through your financial adviser, through your broker-dealer, directly from the Fund by writing to the Fund at Loomis Sayles Funds, P.O. Box 219594, Kansas City, MO 64121-9594, by exchange, by wire, by internet at www.loomissayles.com, by telephone at 800-633-3330, through the Automated Clearing House system, or, in the case of redemptions, by the Systematic Withdrawal Plan. Tax Information Fund distributions are generally taxable to you as ordinary income or capital gain, except for distributions to retirement plans and other investors that qualify for tax-exempt treatment under U.S. federal income tax law generally. Investments in such tax-advantaged plans will generally be taxed only upon withdrawal of monies from the tax-exempt arrangement. 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 may pay the intermediary for the sale of the Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

M-LSUSCG77-0213

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