Weapons of mass destruction (WMD) are among the most frightening of all disasters, impacting hundreds to thousands of people. The effects of such disasters can be both immediate and long-term. This chapter outlines various medical aspects of WMD, such as the widespread and devastating destructive power, the detection of chemical and biologic agents, and the radiation effects of nuclear weapons that are colorless and odorless. There are several important considerations to be taken when responding to WMD disasters that include: (1) personal and public safety; (2) containment of the hazard and control access; (3) implementation of appropriate incident command system (ICS) response; (4) triage and treatment of casualties; and (5) protection of the crime scene. Tables and references