The first paper defines "terrorism" as "a policy by crime" and places it in the category of a "crime against mankind." The criminal nature of terrorism is illustrated with profiles of national and international offenses. The second paper advocates a "three-dimensional" approach to the conceptualization of terrorism. The author views it from political, sociopsychological, and decisionmaking perspectives. The third paper examines the problems and definition of terrorism as well as the sources and characteristics of its major participants (individuals and groups). The authors conclude that there are distinctions between European and non-European terrorism according to their ITERATE data. The fourth paper asserts that there must be distinct differences between terrorism, common crime, and war crime and private or nonstate terrorism; also, terrorism must be categorized by its motivations. The author urges policymakers to be attentive to physical threat, political problems, needed responses, and the role of international law in dealing with terrorism. Notes and tables