The investment seeks current income that is substantially exempt from federal income tax; total return with relatively low volatility of principal is a secondary objective. The fund normally invests at least 80% of its net assets in municipal bonds and debentures, the interest from which is exempt from federal income tax. It invests in a broadly diversified portfolio of municipal obligations issued by governmental authorities throughout the U.S. and its territories. The fund may invest in all types of municipal obligations, including pre-refunded bonds, general obligation bonds, revenue bonds, municipal lease participations and tax-exempt commercial paper.