Under normal market conditions, the Fund invests at least 80 percent of the sum of its net assets and the amount of any borrowings for investment purposes in municipal bonds that pay interest that is exempt from regular federal income tax. Regular federal income tax is different from, and does not include, the federal alternative minimum tax. These municipal bonds include obligations issued by U.S. states and their subdivisions, authorities, instrumentalities and corporations, as well as obligations issued by U.S. territories (such as Puerto Rico, the U.S. Virgin Islands and Guam) that pay interest that is exempt from regular federal income tax. The Fund may invest without limit in municipal bonds that generate income subject to the alternative minimum tax on individuals. Income received from the Funds municipal bonds may affect the federal corporate alternative minimum tax for certain corporations. The Fund is a long-term bond fund and, as such, will generally maintain, under normal market conditions, an investment portfolio with an overall weighted average maturity of greater than 10 years.