The investment seeks to maximize current interest income that is excluded from gross income for regular federal income tax purposes to the extent consistent with prudent investment management and preservation of capital. The fund normally invests at least 80% of its assets in municipal securities and other investments with similar economic characteristics, the interest on which is exempt from regular federal income tax but which may be subject to the federal alternative minimum tax. It normally invests in intermediate-term and long-term municipal securities that have remaining maturities from one to more than thirty years at the time of purchase.