Strategy. Principal investments Under normal circumstances, the fund invests at least 80% of its net assets (plus the amount of any borrowing for investment purposes) in municipal fixed income investments, the income from which is exempt from regular federal income taxes. The fund invests principally in investment grade municipal bonds of varying maturities. Normally, the fund limits its investments in municipal bonds that are subject to the federal alternative minimum tax ("AMT") so that not more than 25% of its interest income will be subject to the AMT, and invests in these bonds when its investment advisor believes that they offer attractive yields relative to similar municipal bonds that are not subject to the AMT. The fund normally limits its portfolio … Show more… Principal investments Under normal circumstances, the fund invests at least 80% of its net assets (plus the amount of any borrowing for investment purposes) in municipal fixed income investments, the income from which is exempt from regular federal income taxes. The fund invests principally in investment grade municipal bonds of varying maturities. Normally, the fund limits its investments in municipal bonds that are subject to the federal alternative minimum tax ("AMT") so that not more than 25% of its interest income will be subject to the AMT, and invests in these bonds when its investment advisor believes that they offer attractive yields relative to similar municipal bonds that are not subject to the AMT. The fund normally limits its portfolio duration to between three and seven years. Duration is a measure of the fund's exposure to interest rate riska longer duration means that changes in market interest rates are likely to have a larger effect on the value of the fund's portfolio. The fund may invest up to 50% of its total assets in municipal bonds that are secured by revenues from public housing authorities and state and local housing finance authorities, including bonds that are secured or backed by the US Treasury or other US government guaranteed securities. There are different types of US government securities, including those issued or guaranteed by the US government, its agencies and its instrumentalities, and they have different types of government support. Some are supported by the full faith and credit of the US, while others are supported by (1) the ability of the issuer to borrow from the US Treasury; (2) the credit of the issuing agency, instrumentality or government-sponsored entity; (3) pools of assets, such as mortgages; or (4) the US government in some other way. The fund limits its investments in municipal bonds with the lowest investment grade rating (or unrated bonds of equivalent quality) to 15% of its total assets at the time the bonds are purchased. Municipal bonds that are downgraded to a below investment grade rating (or equivalent quality) after the initial purchase of such bonds may continue to be held in the fund's portfolio. Management process The fund employs a "manager of managers" structure. UBS Asset Management (Americas) LLC ("UBS AM"), the fund's manager and primary provider of investment advisory services, has the ultimate authority, subject to oversight by the fund's board, to oversee the fund's subadvisor(s) and recommend their hiring, termination and replacement, and to allocate assets among the fund's subadvisor(s). UBS AM's investment process begins with subadvisor selection. UBS AM's portfolio management team constructs a list of potential subadvisors based on information primarily from internal sources and the team's collective knowledge of the industry, but also supplemented by external sources. The team then focuses its research on that list to identify a small number of the most attractive candidates. This research includes ana- lyzing the portfolio holdings and/or positioning of a subadvisor's investment strategy to understand whether the allocation of risk and the drivers of alpha are consistent with the subadvisor's investment philosophy and stated strengths. The most attractive sub-set of those subadvisors is then selected for in-depth, on-site due diligence meetings with representatives from the investment, operations and compliance groups within UBS AM. The due diligence information is then synthesized to select the most attractive candidate(s) for the fund, subject to the board's approval. In managing the fund and overseeing the fund's subadvisor(s), UBS AM views its research process as an ongoing one, as the team continually seeks to confirm a subadvisor's investment thesis over the appropriate investment horizon. In general, UBS AM leverages its research and market knowledge to construct funds with exposure to various subadvisors that are expected, in combination, to produce the desired overall fund characteristics. UBS AM's ongoing monitoring and risk management process incorporates daily, weekly, monthly, quarterly and annual responsibilities designed to monitor the drivers of fund risk and performance at the subadvisor level and at the overall fund level. Through this process, UBS AM may adjust a fund's positioning by altering its allocation weights across subadvisors within the fund and/or by changing the specific subadvisors within the fund. The subadvisor utilizes a strategy that involves investing in undervalued sectors, geographical regions or individual securities. Show less