MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund

MainStay High Yield Corporate Bond Fund

Investment Objective

The Fund seeks maximum current income through investment in a diversified portfolio of high-yield debt securities.

Capital appreciation is a secondary objective.

Fees and Expenses of the Fund

The table below 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 MainStay High Yield Corporate Bond Fund	Class R6
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of the original offering price or redemption proceeds)	none

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

Annual Fund Operating Expenses		Class R6
Management Fees (as an annual percentage of the Fund's average daily net assets)	^[1]	0.55%
Distribution and/or Service (12b-1) Fees		none
Other Expenses		0.04%
Total Annual Fund Operating Expenses		0.59%

[1]

The management fee is as follows: 0.60% on assets up to $500 million; 0.55% on assets from $500 million to $5 billion; 0.525% on assets from $5 billion to $7 billion; and 0.50% on assets in excess of $7 billion, plus a fee for fund accounting services previously provided by New York Life Investment Management LLC under a separate fund accounting agreement. This addition to the management fee amounted to 0.01% of the Fund's average daily net assets, but did not result in a net increase in Total Annual Fund Operating Expenses.

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 that the Fund's operating expenses remain the same.

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, With Redemption, 1 Year	Expense Example, With Redemption, 3 Years	Expense Example, With Redemption, 5 Years	Expense Example, With Redemption, 10 Years
Class R6	60	189	329	738

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 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 29% of the average value of its portfolio.

Principal Investment Strategies

The Fund, under normal circumstances, invests at least 80% of its assets (net assets plus any borrowings for investment purposes) in high-yield corporate debt securities, including all types of high-yield domestic and foreign corporate debt securities that are rated below investment grade by an independent rating agency, such as Standard & Poor's or Moody's Investors Service, Inc., or that are unrated but are considered to be of comparable quality by MacKay Shields LLC, the Fund's Subadvisor.

Some securities that are rated below investment grade by independent rating agencies are commonly referred to as "junk bonds." These securities are sometimes considered speculative. If independent rating agencies assign different ratings to the same security, the Fund will use the lower rating for purposes of determining the security's credit quality.

The Fund's high-yield investments may also include convertible corporate securities and loan participation interests (e.g., bank debt). The Fund may invest up to 20% of its net assets in common stocks and other equity-related securities.

The Fund may hold cash or invest in short-term instruments during times when the Subadvisor is unable to identify attractive high-yield securities.

In times of unusual or adverse market, economic or political conditions, the Fund may invest without limit in investment grade securities and may invest in U.S. government securities or other high quality money market instruments. Periods of unusual or adverse market, economic or political conditions may exist in some cases, for up to a year. To the extent the Fund is invested in cash, investment grade debt or other high quality instruments, the yield on these investments tends to be lower than the yield on other investments normally purchased by the Fund. Although investing heavily in these investments may help to preserve the Fund's assets, it may not be consistent with the Fund's primary investment objective and may limit the Fund's ability to achieve a high level of income.

Investment Process: The Subadvisor seeks to identify investment opportunities through analyzing individual companies and evaluates each company's competitive position, financial condition, and business prospects. The Fund only invests in companies in which the Subadvisor has judged that there is sufficient asset coverage—that is, the Subadvisor's subjective appraisal of a company's value divided by the value of its debt, with the intent of maximizing default-adjusted income and returns.

The Subadvisor may sell a security if it no longer believes the security will contribute to meeting the investment objectives of the Fund. In considering whether to sell a security, the Subadvisor may evaluate, among other things, meaningful changes in the issuer's financial condition and competitiveness.

Principal Risks

Loss of Money Risk: Before considering an investment in the Fund, you should understand that you could lose money.

Market Changes Risk: The value of the Fund's investments may change because of broad changes in the markets in which the Fund invests, which could cause the Fund to underperform other funds with similar objectives. From time to time, markets may experience periods of acute stress that may result in increased volatility. Such market conditions tend to add significantly to the risk of short-term volatility in the net asset value of the Fund's shares.

Management Risk: The investment strategies, practices and risk analysis used by the Subadvisor may not produce the desired results.

Debt Securities Risk: The risks of investing in debt securities include (without limitation): (i) credit risk, i.e., the issuer may not repay the loan created by the issuance of that debt security; (ii) maturity risk, i.e., a debt security with a longer maturity may fluctuate in value more than one with a shorter maturity; (iii) market risk, i.e., low demand for debt securities may negatively impact their price; (iv) interest rate risk, i.e., when interest rates go up, the value of a debt security goes down, and when interest rates go down, the value of a debt security goes up; (v) selection risk, i.e., the securities selected by the Subadvisor may underperform the market or other securities selected by other funds; and (vi) call risk, i.e., during a period of falling interest rates, the issuer may redeem a security by repaying it early, which may reduce the Fund’s income if the proceeds are reinvested at lower interest rates.

Interest rates in the United States are at, or near, historic lows, which may increase the Fund’s exposure to risks associated with rising rates. Moreover, rising interest rates may lead to decreased liquidity in the bond markets, making it more difficult for the Fund to sell its bond holdings at a time when theSubadvisor might wish to sell. Decreased market liquidity also may make it more difficult to value some or all of the Fund’s bond holdings. Please see “Liquidity and Valuation Risk” below for more information.

High-Yield Securities Risk: Investments in high-yield securities or non-investment grade securities (commonly referred to as "junk bonds") are sometimes considered speculative because they present a greater risk of loss than higher quality securities. Such securities may, under certain circumstances, be less liquid than higher rated securities. These securities pay investors a premium (a high interest rate or yield) because of the increased risk of loss. These securities can also be subject to greater price volatility. In times of unusual or adverse market, economic or political conditions, these securities may experience higher than normal default rates.

Liquidity and Valuation Risk: Securities purchased by the Fund that are liquid at the time of purchase may subsequently become illiquid due to, among other things, events relating to the issuer of the securities, market events, economic conditions, investor perceptions or lack of market participants. The lack of an active trading market may make it difficult to obtain an accurate price for a security. If market conditions make it difficult to value securities, the Fund may value these securities using more subjective methods, such as fair value pricing. In such cases, the value determined for a security could be different than the value realized upon such security's sale. Please see “Fair Valuation and Portfolio Holdings Disclosure – Determining the MainStay Funds’ Share Prices and the Valuation of Securities” in the Shareholder Guide for more information. As a result, an investor could pay more than the market value when buying Fund shares or receive less than the market value when selling Fund shares. Liquidity risk may also refer to the risk that the Fund may not be able to pay redemption proceeds within the allowable time period because of unusual market conditions, unusually high volume of redemptions, or other reasons. To meet redemption requests, the Fund may be forced to sell securities at an unfavorable time and/or under unfavorable conditions.

Loan Participation Interest Risk: There may not be a readily available market for loan participation interests, which in some cases could result in the Fund disposing of such a security at a substantial discount from face value or holding such a security until maturity. In addition, there is also the credit risk of the underlying corporate borrower as well as the lending institution or other participant from whom the Fund purchased the loan participation interests.

Floating Rate Loans Risk: The floating rate loans in which the Fund invests are usually rated below investment grade (commonly referred to as "junk bonds") and are generally considered speculative because they present a greater risk of loss, including default, than higher quality debt securities. Moreover, such securities may, under certain circumstances, be less liquid than higher quality debt securities. Although certain floating rate loans are collateralized, there is no guarantee that the value of the collateral will be sufficient to repay the loan. In times of unusual or adverse market, economic or political conditions, floating rate loans may experience higher than normal default rates. In the event of a recession or serious credit event, among other eventualities, the Fund's investments in floating rate loans are more likely to decline.

Convertible Securities Risk: Convertible securities may be subordinate to other securities. In part, the total return for a convertible security depends upon the performance of the underlying stock into which it can be converted. Also, issuers of convertible securities are often not as strong financially as those issuing securities with higher credit ratings, are more likely to encounter financial difficulties and typically are more vulnerable to changes in the economy, such as a recession or a sustained period of rising interest rates, which could affect their ability to make interest and principal payments. If an issuer stops making interest and/or principal payments, the Fund could lose its entire investment.

Foreign Securities Risk: Investments in foreign securities may be riskier than investments in U.S. securities. Differences between U.S. and foreign regulatory regimes and securities markets, including less stringent investor protections and disclosure standards of some foreign markets, less liquid trading markets and political and economic developments in foreign countries, may affect the value of the Fund's investments in foreign securities. Foreign securities may also subject the Fund's investments to changes in currency rates. These risks may be greater with respect to securities of companies that conduct their business activities in emerging markets or whose securities are traded principally in emerging markets.

Equity Securities Risk: Investments in common stocks and other equity securities are particularly subject to the risk of changing economic, stock market, industry and company conditions and the risks inherent in the portfolio manager's ability to anticipate such changes that can adversely affect the value of the Fund's holdings. Opportunity for greater gain often comes with greater risk of loss.

Past Performance

The following bar chart and tables indicate some of the risks of investing in the Fund. The bar chart shows you how the Fund's calendar year performance has varied over the last ten years. The average annual total returns table shows how the Fund's average annual total returns (before and after taxes) for the one-, five- and ten-year periods compare to those of a broad-based securities market index. The Fund has selected the Credit Suisse High Yield Indexas its primary benchmark. The Credit Suisse High Yield Index is a market-weighted index that includes publicly traded bonds rated below BBB by S&P and Baa by Moody's.

Performance data for the classes varies based on differences in their fee and expense structures. Performance figures for Class R6 shares, first offered on June 17, 2013, include the historical performance of Class I shares. Performance for Class I shares, which were first offered on January 2, 2004, include the historical performance of Class B shares through January 1, 2004, adjusted for differences in fees and expenses. Unadjusted, the performance for Class I shares would likely have been different. Performance for Class R6 shares would also likely have been different because of expenses attributable to each share class. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Please visit mainstayinvestments.com for more recent performance information.

The bar chart shows you how the Fund's calendar year performance has varied over the last ten years.

Annual Returns, Class R6 Shares (by calendar year 2003-2012)

Best Quarter
2Q/09	17.34	%
Worst Quarter
4Q/08	-17.22	%

As of March 31, 2013, the Class R6 shares of the Fund would have had a year-to-date return of 2.61%.

Average Annual Total Returns (for the periods ended December 31, 2012)

Average Annual Total Returns	Average Annual Returns, Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
Class R6	Class R6 Return Before Taxes	13.27%	7.97%	10.47%
Class R6 After Taxes on Distributions	Class R6 Return After Taxes on Distributions	10.45%	5.07%	7.53%
Class R6 After Taxes on Distributions and Sales	Class R6 Return After Taxes on Distributions and Sale of Fund Shares	8.54%	5.03%	7.32%
Credit Suisse High Yield Index	Credit Suisse High Yield Index (reflects no deductions for fees, expenses, or taxes)	14.71%	9.53%	10.25%

After-tax returns are calculated using the highest individual federal marginal income tax rates in effect at the time of each distribution or capital gain or upon the sale of fund shares, and do not reflect the impact of state and local taxes. In some cases, the return after taxes may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of shares at the end of the measurement period. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns are not relevant if you hold your shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns shown are for Class R6 shares. After-tax returns for the other share classes may vary.