The fund primarily focuses on investing at least 80% of its capital in municipal bonds. These fixed-income instruments are selected because their interest income is, as determined by the issuer's bond counsel at the time of issue, exempt from federal income tax. The fund has no restrictions on the amount it can allocate to higher-rated municipal debt. Additionally, it may dedicate up to 30% of its assets to "private activity" bonds, the interest from which is considered a tax preference item for federal Alternative Minimum Tax (AMT) calculations.