The fund primarily invests in investment-grade debt securities and, under normal market conditions, will invest at least 80% of its net assets in debt securities with interest payments exempt from federal income tax. The fund's weighted average maturity will be not less than three years nor more than ten years. However, there is no maturity limit on individual securities. The portfolio managers also may buy investment-grade debt securities with interest payments exempt from regular federal income tax, but not exempt from the federal alternative minimum tax.