MainStay DefinedTerm Municipal Opportunities Fund (“MMD”) Declares Initial Monthly Distribution for September

NEW YORK, August 10, 2012 — MainStay DefinedTerm Municipal Opportunities Fund (the "Fund"), a recently organized, diversified, closed-end management investment company (NYSE:MMD), today announced its initial monthly distribution for September. This distribution is the first following the Fund's initial public offering on June 26, 2012 that raised approximately $564 million, assuming full exercise of the underwriters' overallotment option, which may not occur.

The Fund's September distribution is listed below. The following dates apply to today's distribution declaration:

Ex-Date Record Date Payable Date Amount
9/12/2012 9/14/2012 9/28/2012 $0.0958

At the Fund's initial offering price of $20.00 per share, this monthly dividend rate represents an annualized distribution yield of approximately 5.75%. Going forward, it is anticipated that the Fund will declare monthly dividends on the first business day of each month with a payment date on the last business day of the month. The next monthly dividend is expected to be declared on or about October 1, 2012 and be payable on or about October 31, 2012. The amount of monthly distributions may vary, depending on a number of factors. As portfolio and market conditions change, the rate of distributions on the common shares may change. There can be no assurance that the Fund will be able to declare a distribution in each period.

The Fund's primary investment objective is to seek current income exempt from regular U.S. Federal income taxes (but which may be includable in taxable income for purposes of the Federal alternative minimum tax). The Fund has a secondary objective of total return. The Fund seeks to achieve its investment objective by investing, under normal market conditions, at least 80% of its managed assets in municipal bonds, the interest on which is, in the opinion of bond counsel to the issuers, excludable from gross income for regular U.S. Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). There can be no assurance that the Fund's investment objectives will be achieved.

The Fund's daily New York Stock Exchange closing prices, net asset values per share, as well as other information, are available at or by calling the Fund's shareholder servicing agent at (855) 456-9683.

About MainStay Investments
With over $61.6 billion in assets under management, as of June 30, 2012, MainStay Investments is the mutual fund distribution arm of New York Life. MainStay provides financial advisors access to a powerful mix of autonomous, institutional investment managers, delivered by people who understand the needs of today's financial advisor. MainStay has been designated a top three fund family* by Barron's for the 10-year time period for three consecutive years (as of 12/31/11, out of 45 mutual fund families). As an indirect subsidiary of New York Life Insurance Company, a Fortune 100 company founded in 1845, MainStay is owned by the largest mutual life insurance company in the United States** and one of the largest life insurers in the world.

About MacKay Shields
MacKay Shields LLC ("MacKay") serves as the Fund's investment sub-advisor. MacKay is an indirect wholly-owned subsidiary of New York Life Insurance Company and a wholly-owned subsidiary of New York Life Investment Management Holdings LLC. MacKay is a multi product investment management firm with approximately $67.6 billion in assets under management as of June 30, 2012. MacKay manages a number of fixed income strategies for institutional clients and retail mutual funds, including: high yield, high yield active core, core plus, global fixed income, municipal and investment grade. MacKay also manages convertible strategies.

Past performance is no assurance of future results. Investment return and market value of an investment in the Fund will fluctuate. Shares, when sold, may be worth more or less than their original cost.

This material may include statements that constitute "forward-looking statements" under the U.S. securities laws. Forward-looking statements include, among other things, projections, estimates and information about possible or future results or events related to the Fund, market or regulatory developments. The views expressed herein are not guarantees of future performance or economic results and involve certain risks, uncertainties and assumptions that could cause actual outcomes and results to differ materially from the views expressed herein. The views expressed herein are subject to change at any time based upon economic, market, or other conditions and the Fund undertakes no obligation to update the views expressed herein.

*Barron's Annual Ranking of mutual fund families (February 6, 2012). To qualify for the Lipper/Baron's Fund Survey, a fund family must have at least three funds in Lipper's general U.S. stock category, one in world equity, one mixed equity fund, at least two taxable bond funds, and one tax-exempt offering. Each fund's returns are adjusted for 12b-1 fees. Fund loads, or sales charges, are not included in the calculation of returns. Each fund's return is measured against those of all the funds in its Lipper category.

**Based on revenue as reported by "Fortune 500 ranked within Industries, Insurance: Life, Health (Mutual)," Fortune magazine, May 21, 2012.

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Allison Scott

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