In 1998, the Department of Defense (DoD) began a program of mandatory immunization against anthrax for all military personnel. As the program proceeded, however, some military personnel and their families raised concerns about the safety and efficacy of the anthrax vaccine. Acknowledging both the need to protect military personnel and the concerns about the anthrax vaccine, Congress directed the Centers for Disease Control and Prevention (CDC) to carry out a research program on its safety and efficacy. To assist in the development of this program, CDC requested the Institute of Medicine to convene a committee to review the completeness and appropriateness of the research program. In An Assessment of the CDC Anthrax Vaccine Safety and Efficacy Research Program, the committee makes an overall assessment of the CDC research plan and reviews the specific studies proposed by CDC in the three areas of efficacy, safety, and acceptability. The committee also notes additional research needs that became evident following the bioterrorist events of 2001 and makes recommendations about the leadership of the research program.