Weapons of mass destruction (WMDs) are capable of producing massive casualties and are typically grouped into nuclear, biologic, and chemical weapons. In the wake of the September 11th disasters, attention to terrorist groups and the potential for use of WMDs has increased. Biologic and chemical weapons are relatively accessible and inexpensive to develop, and are thought to be the most available to foreign states and subnational terrorist groups. This article reviews various biologic and chemical weapons, including emergency diagnosis and management of selected agents.