As the nation prepares itself for future terrorist attacks, the questions are endless and the answers elusive. How can American cities prevent or, if need be, respond to a man-made smallpox epidemic, a sudden outbreak of tularemia, a bomb studded with radioactive material, or a poisoned water supply? After Sept. 11 and the fall anthrax attacks, Dean Alfred Sommer dedicated the School's science and collective expertise to help a nation stunned by terrorism. School faculty, students, and alumni have taken up the challenge. Long a proponent of biopreparedness, the Center for Civilian Biodefense Strategies is counseling government officials and guiding the national preparations with science-based advice. The Hopkins Public Health Scientists Working to Address Terrorism (SWAT) team has united School faculty in the pursuit of research and policy that can blunt terror's power. This Special Report chronicles their contributions to the science of security.