The heaviest use of State terrorism occurred in immediately postrevolutionary Second World societies like the Soviet Union and Eastern European countries. These countries make less use of it today, however. Many Third World societies in the contemporary era also use terrorism extensively. In general, the liberal democracies that constitute the First World make little use of terror as a means of governance, although it has been used in some of these countries. The size of the target population is extremely broad where State terrorism occurs at all extensively in the Third World; it was also large in the early postrevolutionary Second World. In those contexts, much of society has been governed, at least in part, by State terrorism. Elsewhere it governs relatively small segments of the population. In the Third World, the target population is only vaguely defined as a potential political opposition. In contrast, in the early postrevolutionary Second World, the target population was more clearly defined as nonrevolutionary classes and the membership of the revolutionary party. Where the scope of State terrorism is limited, the targets are socially isolated and generally distrusted groups. In the Second World, therefore, the dissident intelligentsia is the main target of State terrorism. Using the concepts of probabilities of relative costs and relative effectiveness of terrorism, it is possible to identify the syndromes which, if present, produce conditions conducive to State terrorism. Tables, notes, and 53 references are provided.