Under certain conditions, the interest from bonds issued by states, cities, and certain other government agencies is exempt from federal income taxes. In many states, the interest from tax-exempt bonds will also be exempt from state and local income taxes. If you sell a tax-exempt bond at a profit, you could incur capital gains taxes. Some tax-exempt bond interest could be subject to the federal alternative minimum tax. The principal value of bonds fluctuates with market conditions. Bonds sold prior to maturity may be worth more or less than their original cost.