Although terrorist tactics have been used throughout recorded history, terrorism has grown markedly since the late 1960's. Political terrorism, which is used to achieve political objectives, ranges from actions initiated by an individual or group controlled by a nation that occur outside that nation to actions initiated by an individual or group of nationals within their own nation. Among the political developments which have caused the current wave of terrorism are the decision by some Palestinian factions to move the focus of their attacks outside Israel, the intensification of urban guerrilla warfare in several Latin American countries, the radical student movements of the 1960's, and regional conflicts. The five types of politically motivated terrorist groups are the ethnic separatist movements, nationalist movements, ideological extremist groups, issue-oriented interest groups, and sociopathic individuals and groups. While airline hijackings and barricade-hostage incidents have declined, bombings, armed attacks, assassinations, and kidnappings have stayed stable or increased. The largest percentage of incidents between 1968 and 1978 occurred in Western Europe. However, U.S. citizens and property have frequently been targets. Domestic and transnational terrorist groups have cooperated in training, weapons exchange, coordination, and other areas. Some governments have also cooperated with terrorist groups. A multiple-response approach is needed to deal with the proliferation of terrorist incidents. Tables and 31 reference notes are included.