In the fall of 2001, letters containing anthrax spores were mailed to news media personnel and congressional officials, leading to the first cases of anthrax infection related to an intentional release of anthrax in the United States. Outbreaks of anthrax infection were concentrated in six locations, or epicenters, in the country. An examination of the public health response to the anthrax incidents provides an important opportunity to apply lessons learned from that experience to enhance the nation's preparedness for bioterrorism. Because of its interest in bioterrorism preparedness, Congress asked GAO to review the public health response to the anthrax incidents. Specifically, GAO determined (1) what was learned from the experience that could help improve public health preparedness at the local and state levels and (2) what was learned that could help improve public health preparedness at the federal level and what steps have been taken to make those improvements.