The typology of terrorism presented here includes nonpolitical terrorism, quasi-terrorism, limited political terrorism, official or state terrorism, and political terrorism. The defining characteristics of modern terrorism include jet air travel, high- technology weaponry, telecommunications, and the mass media's role in drawing public attention to terrorist causes. The upsurge of modern international terrorism in recent years and its probable continuation into the next century are attributable to the fact that, in modern societies, terrorism is effective, is highly cost- effective, is an accepted form of low-intensity warfare, and is seen as one of the few avenues of action by minority groups trying to establish national rights. The article discusses the role of the U.S. as a target for terrorists, probable trends in terrorism, the probabilities of terrorists' use of a nuclear or biological weapon, the impact of American counterterrorist measures, and the effect of terrorism on democracy and the rule of law. 57 notes