Until the 1970s, smallpox was feared worldwide for the significant morbidity and mortality it caused. Although naturally occurring disease has been eliminated, the virus itself has not been destroyed, and it is assumed that some of the variola stored in the former Soviet Union has been removed. The majority of the world's population is susceptible to smallpox because vaccination ended in 1972 in the United States and in the rest of the world in 1982. A major epidemic could result if there was an intentional release of smallpox. Variola is both durable and highly infective, 2 features that make it an attractive bioweapon. Because of this threat, physicians should be familiar with the clinical features of smallpox and the appropriate isolation and medical response procedures. Although there is a vaccine that can provide pre- and postexposure protection, the vaccination itself is not without risks. There is no effective therapy for smallpox and studies of new treatments are underway.