Structural theories are one of the three categories of theories that explain the most prominent causes of this terrorism. The other two types are psychological and rational choice theories. The analysis considers case studies of countries that have experienced terrorism and movements that consistently relied on the use of terrorism to achieve their political objectives. The resulting factors are integrated into categories, and propositions concerning interactions are presented. A sketch of a general structural model of the conditions of terrorism is then presented as a better foundation than other models for the qualitative and quantitative analysis of the causes of terrorism. The model includes factors such as social, cultural, and historical facilitation; organizational development or split; the presence of other forms of political unrest; support from a variety of sources; the failure of counterterrorist organizations; the availability of weapons and explosives; and grievances. Figure, notes, and 47 references (Author abstract modified)