Describes the origin, topics, and important findings. Researchers representing a variety of disciplines have studied the motivation and tactics of international terrorists; the use of computers to help manage low-level crises; policy and tactics for dealing with terrorists holding hostages; U.S. military capabilities for subconventional missions such as rescuing U.S. nationals abroad; and the potential for sabotage of U.S. nuclear facilities and for nuclear action by extremists. Terrorist incidents are increasing. Terrorist groups have found such tactics effective in attracting worldwide attention and in achieving limited goals — with a surprisingly low risk of capture or punishment. Among the societal consequences have been (1) a large diversion of public and private resources to internal security, (2) a trend toward authoritarian regimes using repression and surveillance to protect their citizens, and (3) the likelihood of greater instability and disruption in the world despite conditions of formal peace among nations.