MainStay Unconstrained Bond Fund		Summary Prospectus February 28, 2017
Class/Ticker	A MASAXInvestor MSYDXB MASBXC MSICXI MSDIXR2 MSIRXR3 MSDJX

To Statutory ProspectusTo Statement of Additional Information

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 by going online to mainstayinvestments.com/documents, by calling 800-MAINSTAY (624-6782) or by sending an e-mail to MainStayShareholderServices@nylim.com. The Fund's Prospectus and Statement of Additional Information, both dated February 28, 2017, as may be amended from time to time, are incorporated by reference into this Summary Prospectus.

Investment Objective

The Fund seeks total return by investing primarily in domestic and foreign debt securities.

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. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the MainStay Funds. This amount may vary depending on the MainStay Fund in which you invest. In addition, different financial intermediary firms and financial professionals may impose different sales loads and waivers. More information about these and other discounts or waivers is available from your financial professional; in the "Information on Sales Charges" section starting on page 117 of the Prospectus and Appendix A – Intermediary-Specific Sales Charge Waivers and Discounts; and in the "Alternative Sales Arrangements" section on page 109 of the Statement of Additional Information.

		Class A		Investor  Class		Class B1		Class C		Class I		Class R2		Class R3
Shareholder Fees (fees paid directly from your investment)
	Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.50	%	4.50	%	None		None		None		None		None
	Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of the original offering price or redemption proceeds)	None	2	None	2	5.00	%	1.00	%	None		None		None
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
	Management Fees (as an annual percentage of the Fund's average daily net assets)3	0.56	%	0.56	%	0.56	%	0.56	%	0.56	%	0.56	%	0.56	%
	Distribution and/or Service (12b-1) Fees	0.25	%	0.25	%	1.00	%	1.00	%	None		0.25	%	0.50	%
	Other Expenses
	Interest Expense on Securities Sold Short	0.11	%	0.11	%	0.11	%	0.11	%	0.11	%	0.11	%	0.11	%
	Broker Fees and Charges on Short Sales	0.05	%	0.05	%	0.05	%	0.05	%	0.05	%	0.05	%	0.05	%
	Remainder of Other Expenses	0.19	%	0.21	%	0.21	%	0.21	%	0.19	%	0.31	%	0.28	%
	Total Other Expenses	0.35	%	0.37	%	0.37	%	0.37	%	0.35	%	0.47	%	0.44	%
	Total Annual Fund Operating Expenses	1.16	%	1.18	%	1.93	%	1.93	%	0.91	%	1.28	%	1.50	%

1.Class B shares are closed to all new purchases as well as additional investments by existing Class B shareholders.

2. A contingent deferred sales charge of 1.00% may be imposed on certain redemptions made within 24 months of the date of purchase on shares that were purchased without an initial sales charge.

3.The management fee is as follows: 0.60% on assets up to $500 million; 0.55% on assets from $500 million up to $1 billion; 0.50% on assets from $1 billion to $5 billion; and 0.475% on assets in excess of $5 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 whether or not you redeem all of your shares at the end of those periods (except as indicated with respect to Class B and Class C shares). The Example reflects Class B shares converting into Investor Class shares in years 9-10; fees could be lower if you are eligible to convert to Class A shares instead. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The Example reflects the contractual fee waiver and/or expense reimbursement arrangement, if applicable, for the current duration of the arrangement only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expenses After	Class A	Investor	Class B		Class C		Class I	Class R2	Class R3
		Class	Assuming no redemption	Assuming redemption at end of period	Assuming no redemption	Assuming redemption at end of period
1 Year	$      563	$      565	$      196	$      696	$      196	$      296	$        93	$      130	$      153
3 Years	$      802	$      808	$      606	$      906	$      606	$      606	$      290	$      406	$      474
5 Years	$   1,060	$   1,070	$   1,042	$   1,242	$   1,042	$   1,042	$      504	$      702	$      818
10 Years	$   1,796	$   1,817	$   2,059	$   2,059	$   2,254	$   2,254	$   1,120	$   1,545	$   1,791

(NYLIM) NL052 MSUB01-02/17

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 15% of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objective through a flexible investment process that allocates investments across the global fixed-income markets. The Fund, under normal circumstances, invests at least 80% of its assets (net assets plus any borrowings for investment purposes) in a diversified portfolio of debt or debt-related securities such as: debt or debt-related securities issued or guaranteed by the U.S. or foreign governments, their agencies or instrumentalities; obligations of international or supranational entities; debt or debt-related securities issued by U.S. or foreign corporate entities; zero coupon bonds; municipal bonds; mortgage-related and other asset-backed securities; loan participation interests; convertible bonds; and variable or floating rate debt securities. The Fund may invest in debt securities that are rated investment grade and below investment grade by an independent rating agency. Securities that are rated below investment grade by independent rating agencies are commonly referred to as “high-yield securities” or “junk bonds.” 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 securities may be denominated in U.S. or foreign currencies, and may have fixed, variable, floating or inverse floating rates of interest. The Fund may invest without limitation in securities of foreign issuers, including emerging markets. The currency exposure of non-U.S. investments may or may not be hedged. The Fund may invest up to 15% of its net assets in equity securities.

The Fund intends to utilize various investment strategies in a broad array of fixed-income sectors to achieve its investment objective. The Fund will not be constrained by portfolio management relative to an index. Because an unconstrained bond portfolio does not track a fixed-income index, its performance may vary at times and demonstrate low correlation to traditional fixed-income indices. In pursuing its investment objective, the Fund’s investment strategy is subject to market risk and shares may gain or lose value.

The average portfolio duration of the Fund will normally vary from 0 to 7 years. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates. The longer a security’s duration, the more sensitive it will be to changes in interest rates.

The Fund may invest in derivatives, such as futures, options, forward commitments and interest rate swap agreements to try to enhance returns or reduce the risk of loss by hedging certain of its holdings or manage duration. The Fund may invest up to 25% of its total assets in swaps.

The Fund may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The Fund's short positions, either direct short positions or through credit default swaps or total return swaps, may total up to 20% of the Fund’s net assets. The Fund may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

Investment Process: MacKay Shields LLC, the Fund’s Subadvisor, seeks to identify investment opportunities through an investment process focused on macroeconomic analysis and bottom-up security selection. The Subadvisor allocates the Fund's investments among the various bond market sectors based on current and projected economic and market conditions. The Fund may invest across bond market sectors, geographies and credit qualities.

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

Principal Risks

You can lose money by investing in the Fund. An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. The investments selected by the Fund’s Subadvisor may underperform the market or other investments. The Fund may receive large purchase or redemption orders which may have adverse effects on performance if the Fund were required to sell securities, invest cash or hold cash at times when it would not otherwise do so.

The principal risks of investing in the Fund are summarized below.

Market Risk: The value of the Fund's investments may fluctuate because of changes in the markets in which the Fund invests, which could cause the Fund to underperform other funds with similar objectives. Changes in these markets may be rapid and unpredictable. From time to time, markets may experience periods of stress for potentially prolonged periods that may result in: (i) increased market volatility; (ii) reduced market liquidity; and (iii) increased redemptions. Such conditions may add significantly to the risk of volatility in the net asset value of the Fund's shares.

Portfolio Management Risk: The investment strategies, practices and risk analysis used by the Subadvisor may not produce the desired results. In addition, the Fund may not achieve its investment objective, including during a period in which the Subadvisor takes temporary positions in response to unusual or adverse market, economic or political conditions, or other unusual or abnormal circumstances.

Debt Securities Risk: The risks of investing in debt or fixed-income securities include (without limitation): (i) credit risk, e.g., the issuer or guarantor of a debt security may be unable or unwilling (or be perceived as unable or unwilling) to make timely principal and/or interest payments or otherwise honor its obligations; (ii) maturity risk, e.g., a debt security with a longer maturity may fluctuate in value more than one with a shorter maturity; (iii) market risk, e.g., low demand for debt securities may negatively impact their price; (iv) interest rate risk, e.g., when interest rates go up, the value of a debt security generally goes down, and when interest rates go down, the value of a debt security generally goes up (long-term debt securities are generally more susceptible to interest rate risk than short-term debt securities); and (v) call risk, e.g., 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.

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Interest rates in the United States are near historic lows, which may increase the Fund’s exposure to risks associated with rising interest rates. Interest rates may rise significantly and/or rapidly. Rising interest rates or lack of market participants may lead to decreased liquidity and increased volatility in the bond markets, making it more difficult for the Fund to sell its bond holdings at a time when the Subadvisor might wish to sell. Decreased liquidity in the bond markets also may make it more difficult to value some or all of the Fund’s bond holdings. Additionally, the risks of municipal bonds include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers, and the possibility of future tax and legislative changes, which could affect the market for and value of municipal securities.

Additional risks associated with an investment in the Fund include the following: (i) not all U.S. government securities are insured or guaranteed by the U.S. government—some are backed only by the issuing agency, which must rely on its own resources to repay the debt; and (ii) the Fund's yield will fluctuate with changes in short-term interest rates.

Zero Coupon Bond Risk: Because zero-coupon securities bear no interest and compound semi-annually at the rate fixed at the time of issuance, their value generally is more volatile than the value of other fixed-income securities. An investment in zero-coupon and delayed interest securities may cause the Fund to recognize income, and therefore the Fund may be required to make distributions to shareholders before the Fund receives any cash payments on its investment.

Municipal Bond Risk: Municipal bond risks include the inability of the issuer to repay the obligation, the relative lack of information about certain issuers, and the possibility of future tax and legislative changes, which could affect the market for and value of municipal securities. Municipalities continue to experience economic and financial difficulties in the current economic environment. The ability of a municipal issuer to make payments and the value of municipal bonds can be affected by uncertainties in the municipal securities market. Such uncertainties could cause increased volatility in the municipal securities market and could negatively impact the Fund’s net asset value.

Short Selling Risk: If a security sold short increases in price, the Fund may have to cover its short position at a higher price than the short sale price, resulting in a loss. The Fund may have substantial short positions and must borrow those securities to make delivery to the buyer. The Fund may not be able to borrow a security that it needs to deliver or it may not be able to close out a short position at an acceptable price and may have to sell related long positions before it had intended to do so. Thus, the Fund may not be able to successfully implement its short sale strategy due to limited availability of desired securities or for other reasons. The Fund also may be required to pay a premium and other transaction costs, which would increase the cost of the security sold short. The amount of any gain will be decreased, and the amount of any loss increased, by the amount of the premium, dividends, interest or expenses the Fund may be required to pay in connection with the short sale.

Until the Fund replaces a borrowed security, it is required to maintain a segregated account of cash or liquid assets with the Fund's custodian to cover the Fund's short position. Generally, securities held in a segregated account cannot be sold unless they are replaced with other liquid assets. The Fund's ability to access the pledged collateral may also be impaired in the event the broker fails to comply with the terms of the contract. In such instances the Fund may not be able to substitute or sell the pledged collateral. Additionally, the Fund must maintain sufficient liquid assets (less any additional collateral pledged to the broker), marked-to-market daily, to cover the short sale obligations. This may limit the Fund's investment flexibility, as well as its ability to meet redemption requests or other current obligations. Because losses on short sales arise from increases in the value of the security sold short, such losses are theoretically unlimited. By contrast, a loss on a long position arises from decreases in the value of the security and is limited by the fact that a security's value cannot go below zero.

By investing the proceeds received from selling securities short, the Fund could be deemed to be employing a form of leverage, which creates special risks. The use of leverage may increase the Fund's exposure to long positions and make any change in the Fund's net asset value greater than it would be without the use of leverage. This could result in increased volatility of returns. There is no guarantee that the Fund will leverage its portfolio, or if it does, that the Fund's leveraging strategy will be successful or that it will produce a higher return on an investment.

Regulatory Risk: The Fund as well as the issuers of the securities and other instruments in which the Fund invests are subject to considerable regulation and the risks associated with adverse changes in laws and regulations governing their operations. For example, regulatory authorities in the U.S. or other countries may prohibit or restrict the ability of the Fund to short sell certain securities, either generally or with respect to certain industries or countries, which may impact the Fund's ability to fully implement its investment strategies. In addition, regulatory authorities are in the process of adopting and implementing regulations governing derivatives markets, the ultimate impact of the regulations remains unclear and may adversely affect, among other things, the availability, value or performance of derivatives.

Derivatives Risk: Derivatives are investments whose value depends on (or is derived from) the value of an underlying instrument, such as a security, asset, reference rate or index. Derivative strategies may expose the Fund to greater risk and often involve leverage, which may exaggerate a loss, potentially causing the Fund to lose more money than it would have lost had it invested directly in the underlying instrument. Derivatives may be difficult to sell, unwind or value. Derivatives may also be subject to counterparty risk, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable to honor its contractual obligations to the Fund. Futures may be more volatile than direct investments in the instrument underlying the contract, and may not correlate perfectly to the underlying instrument. Futures and other derivatives also may involve a small initial investment relative to the risk assumed, which could result in losses greater than if they had not been used. Due to fluctuations in the price of the underlying asset, the Fund may not be able to profitably exercise an option and may lose its entire investment in an option. Forward commitments entail the risk that the instrument may be worth less when it is issued or received than the price the Fund agreed to pay when it made the commitment. The use of foreign currency forwards may result in currency exchange losses due to fluctuations in currency exchange rates or an imperfect correlation between portfolio holdings denominated in a particular currency and the forward contracts entered into by the Fund. Swaps are particularly subject to counterparty credit, correlation, valuation, liquidity and leveraging risks. Certain standardized swaps are subject to mandatory central clearing and exchange trading. Central clearing and exchange trading are intended to reduce counterparty credit risk and increase liquidity but does not make swap transactions risk-free. Derivatives may also increase the expenses of the Fund.

High-Yield Securities Risk: Investments in high-yield securities or non-investment grade securities (commonly referred to as "junk bonds") are considered speculative because they present a greater risk of loss than higher quality securities. Such securities may, under certain circumstances, be less liquid than

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higher rated securities. These securities pay investors a premium (a high interest rate or yield) because of the potential illiquidity and 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.

Floaters and Variable Rate Notes Risk: Floaters and variable rate notes provide for a periodic adjustment in the interest rate paid on the securities. The rate adjustment intervals may be regular and range from daily up to annually, or may be based on an event, such as a change in the prime rate. Floating and variable rate notes may be subject to greater liquidity risk than other debt securities, meaning that there may be limitations on the Fund's ability to sell the securities at any given time. Securities with floating interest rates generally are less sensitive to interest rate changes, but may decline in value if their interest rates do not rise as much or as fast as interest rates in general. Such securities also may lose value.

Mortgage Dollar Roll Transaction Risk: A mortgage dollar roll is a transaction in which the Fund sells mortgage-related securities from its portfolio to a counterparty from whom it simultaneously agrees to buy a similar security on a delayed delivery basis. Mortgage dollar roll transactions are subject to certain risks, including the risk that securities returned to the Fund at the end of the roll, while substantially similar, may be inferior to what was initially sold to the counterparty.

Mortgage-Backed/Asset-Backed Securities Risk: Investments in asset-backed securities (such as mortgage-backed securities) generally involve a stream of payments based on the underlying obligations. These payments, which are often part interest and part return of principal, vary based on the rate at which the underlying borrowers repay their loans or other obligations. Asset-backed securities are subject to the risk that borrowers may default on the underlying obligations and that, during periods of falling interest rates, these obligations may be called or prepaid and, during periods of rising interest rates, obligations may be paid more slowly than expected. Impairment of the underlying obligations or collateral, such as by non-payment, will reduce the security's value. Enforcing rights against such collateral in events of default may be difficult or insufficient. The value of these securities may be significantly affected by changes in interest rates, the market's perception of issuers, and the creditworthiness of the parties involved. The ability of the Fund to successfully utilize these instruments may depend on the ability of the Subadvisor to forecast interest rates and other economic factors correctly. These securities may have a structure that makes their reaction to interest rate changes and other factors difficult to predict, making their value highly volatile.

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, or if unrated, determined by the Subadvisor to be of comparable quality (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 particularly susceptible to liquidity and valuation risks. Although certain floating rate loans are collateralized, there is no guarantee that the value of the collateral will be sufficient or available to satisfy the borrower’s obligation. 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 value of the Fund's investments in floating rate loans are more likely to decline. The secondary market for floating rate loans is limited and, thus, the Fund’s ability to sell or realize the full value of its investment in these loans to reinvest sale proceeds or to meet redemption obligations may be impaired. In addition, floating rate loans generally are subject to extended settlement periods that may be longer than seven days. As a result, the Fund may be adversely affected by selling other investments at an unfavorable time and/or under unfavorable conditions or engaging in borrowing transactions, such as borrowing against its credit facility, to raise cash to meet redemption obligations or pursue other investment opportunities.

In certain circumstances, floating rate loans may not be deemed to be securities. As a result, the Fund may not have the protection of the anti-fraud provisions of the federal securities laws. In such cases, the Fund generally must rely on the contractual provisions in the loan agreement and common-law fraud protections under applicable state law.

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.

Emerging Markets Risk: The risks related to investing in foreign securities are generally greater with respect to securities of companies that conduct their business activities in emerging markets or whose securities are traded principally in emerging markets. The risks of investing in emerging markets include the risks of illiquidity, increased price volatility, smaller market capitalizations, less government regulation, less extensive and less frequent accounting, financial and other reporting requirements, risk of loss resulting from problems in share registration and custody, substantial economic and political disruptions and the nationalization of foreign deposits or assets.

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.

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 managers' 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.

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When-Issued Securities Risk: The Fund may agree to purchase a security on a when-issued basis, making a commitment to pay a fixed price for a security when it is issued in the future. The principal risk of transactions involving when-issued securities is that the security will be worth less when it is issued or received than the price the Fund agreed to pay when it made the commitment.

Liquidity and Valuation Risk: Securities purchased by the Fund may be illiquid at the time of purchase or liquid at the time of purchase and subsequently become illiquid due to, among other things, events relating to the issuer of the securities, market events, operational issues, economic conditions, investor perceptions or lack of market participants. The lack of an active trading market may make it difficult to sell or obtain an accurate price for a security. If market conditions or issuer specific developments 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. 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. This could affect the proceeds of any redemption or the number of shares an investor receives upon purchase. 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 or to raise cash to pursue other investment opportunities, the Fund may be forced to sell securities at an unfavorable time and/or under unfavorable conditions, which may adversely affect the Fund.

Money Market/Short-Term Securities Risk: To the extent the Fund holds cash or invests in money market or short-term securities, the Fund may be less likely to achieve its investment objective. In addition, it is possible that the Fund's investments in these instruments could lose money.

Past Performance

The following bar chart and table 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. Sales loads are not reflected in the bar chart. If they were, returns would be less than those shown. 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 as well as two additional benchmarks. The Fund has selected the Bloomberg Barclays U.S. Aggregate Bond Indexas its primary benchmark. The Bloomberg Barclays U.S. Aggregate Bond Index is a broad-based benchmark that measures the investment grade, U.S. dollar-denominated, fixed-rate taxable bond market, including Treasuries, government-related and corporate securities, mortgage-backed securities (agency fixed-rate and hybrid adjustable rate mortgage pass-throughs), asset-backed securities, and commercial mortgage-backed securities. The Fund has selected the BofA Merrill Lynch U.S. Dollar 3-Month LIBOR Constant Maturity Index as its secondary benchmark. The BofA Merrill Lynch U.S. Dollar 3-Month LIBOR Constant Maturity Index represents the London InterBank Offered Rate ("LIBOR") with a constant 3-month average maturity. LIBOR is a composite of interest rates at which banks borrow from one another in the London market, and it is a widely used benchmark for short-term interest rates. The Fund has selected the Morningstar Nontraditional Bond Category Average as an additional benchmark. The Morningstar Nontraditional Bond Category Average contains funds that pursue strategies divergent in one or more ways from conventional practice in the broader bond-fund universe. Morningstar category averages are equal-weighted returns based on constituents of the category at the end of the period.

Performance data for the classes varies based on differences in their fee and expense structures. Performance is not shown for classes with less than one calendar year of performance. 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.

Effective February 28, 2013, the Fund changed its investment strategies. The past performance in the bar chart and table reflect the Fund's prior investment objective and principal investment strategies.

Annual Returns, Class B Shares

(by calendar year 2007-2016)

Best Quarter
3Q/09	9.93	%
Worst Quarter
4Q/08	-7.60	%

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Average Annual Total Returns (for the periods ended December 31, 2016)

				5 Years or		10 Years or
	Inception	1 Year		Since		Since
				Inception		Inception
Return Before Taxes
Class B	2/28/1997	2.23	%	3.23	%	4.06	%
Return After Taxes on Distributions
Class B		0.57	%	1.83	%	2.42	%
Return After Taxes on Distributions and Sale of Fund Shares
Class B		1.23	%	1.88	%	2.48	%
Return Before Taxes
Class A	2/28/1997	3.16	%	3.48	%	4.46	%
Investor Class	2/28/2008	3.08	%	3.39	%	4.43	%
Class C	9/1/1998	6.11	%	3.58	%	4.05	%
Class I	1/2/2004	8.28	%	4.69	%	5.23	%
Class R2	2/28/2014	7.79	%	1.11	%	N/A
Bloomberg Barclays U.S. Aggregate Bond Index (reflects no deductions for fees, expenses, or taxes)		2.65	%	2.23	%	4.34	%
BofA Merrill Lynch U.S. Dollar 3-Month LIBOR Constant Maturity Index (reflects no deductions for fees, expenses, or taxes)		0.66	%	0.38	%	1.28	%
Morningstar Nontraditional Bond Category Average (reflects no deductions for fees and taxes)		5.28	%	2.85	%	3.38	%

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 B shares. After-tax returns for the other share classes may vary.

Management

New York Life Investment Management LLC serves as the Fund's Manager. MacKay Shields LLC serves as the Fund's Subadvisor.

Subadvisor	Portfolio Managers	Service Date
MacKay Shields LLC	Dan Roberts, Executive Managing Director	Since 2009
	Michael Kimble, Senior Managing Director	Since 2009
	Louis N. Cohen, Senior Managing Director	Since 2009

How to Purchase and Sell Shares

You may purchase or sell shares of the Fund on any day the Fund is open for business by contacting your financial adviser or financial intermediary firm, or by contacting the Fund by telephone at 800-MAINSTAY (624-6782), by mail at MainStay Funds, P.O. Box 8401, Boston, MA 02266-8401 or by accessing our website at mainstayinvestments.com. Generally, an initial investment minimum of $1,000 applies if you invest in Investor Class or Class C shares, $25,000 for Class A shares and $5,000,000 for individual investors in Class I shares investing directly (i) with the Fund; or (ii) through certain private banks and trust companies that have an agreement with NYLIFE Distributors LLC, the Fund’s principal underwriter and distributor, or its affiliates. A subsequent investment minimum of $50 applies to investments in Investor Class and Class C shares. However, for Investor Class or Class C shares purchased through AutoInvest, MainStay’s systematic investment plan, a $500 initial investment minimum and a $50 minimum for subsequent purchases applies. Class R2 shares, Class R3 shares and institutional shareholders in Class I shares have no initial or subsequent investment minimums. Class B shares are closed to all new purchases and additional investments.

Certain financial intermediaries through whom you may invest may impose their own investment minimums, fees, policies and procedures for purchasing and selling Fund shares, which are not described in this Prospectus or the Statement of Additional Information, and which will depend on the policies, procedures and trading platforms of the financial intermediary. Consult a representative of your financial intermediary about the availability of shares of the Fund and the intermediary's policies, procedures and other information.

Tax Information

The Fund's distributions are generally taxable to you as ordinary income, capital gains, or a combination of the two, unless you are investing through a tax-deferred arrangement, such as a 401(k) plan or an individual retirement account.

Compensation to Financial Intermediary Firms

If you purchase Fund shares through a financial intermediary firm (such as a broker/dealer or bank), the Fund and its related companies may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the financial intermediary firm or your financial adviser to recommend the Fund over another investment. Ask your financial adviser or visit your financial intermediary firm's website for more information.

To Statutory ProspectusTo Statement of Additional Information

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