The authors first present some biological, social, and psychological constructs that are important in understanding group violence. Biological constructs focus on instinct in the use of violence to obtain resources, violence as the most effective means to group survival, and violence that results from in-group/out-group dynamics. Social and psychological constructs pertain to social learning of violence, psychoanalytical views of violence that emerge from hatred, the role of emotions in violence, group processes involved in violence, moral justification in violence, and the interactions among psychological factors that contribute to violence. A section of the paper that profiles terrorism addresses the impact of terrorism, the definition of "terrorism," and explanations of terrorism. Other major sections of the paper consider motivational profiles of terrorists and solutions to terrorism. On the latter topic, the general principle promoted is that effective counterterrorism strategies will be complex, difficult, expensive, and not always quick to show dramatic results. Such strategies may not have great public appeal, since effective strategies may not be overtly military or produce the violence against terrorists that a vengeful public may demand. The policy must be global, emphasizing international and interagency cooperation in a long-term building of intelligence and response strategies that can be adapted to a wide variety of terrorist threats and challenges. Governments that are actual and potential targets of terrorists should attempt to talk directly with terrorists in an effort to understand their mindset and the basis for their resort to violence. Restraint is necessary to avoid premature action that may prevent the obtaining of further intelligence. Overreaction to the terrorist threat may lead to the erosion of freedom in the arena of a potential terrorist threat, which can in turn undermine the values and legitimacy of the government. The teaching and implementation of values and practices of peacemaking can produce the development and maintenance of social systems that support humane and compassionate behavior. 5 tables and 81 references