It also examines, based on the little primary evidence that is available, what the existence of terrorists is like; what problems and satisfactions they derive from their interpersonal relations; what external problems and internal anxieties they deal with; and what finally leads them, in a few particular cases, to leave the group. The report begins with a brief critical discussion of the existing literature on the terrorist mentality and on the perceived ideological origins of terrorism. It next presents descriptive sketches of the terrorist individual, based on interviews and autobiographical writings. A discussion of how terrorist groups work is next provided. Five former terrorists served as principal sources for the report: Michael Baumann, Hans-Joachim Klein, Zvenco Busic, Kozo Okamoto, and Horst Mahler. The Note concludes that there are many different types of terrorists and that terrorists have at least as many vulnerabilities as have other people and groups. These include lack of trust, many severe pressures, intergroup conflicts, lax leadership and planning, a hardening of Government attitudes, and a loss of sympathizers. Footnotes and a chart of a theoretical model for analysis of terrorists are included. (Author abstract modified).