This summary integrates the findings of seven data- collection and research phases conducted in the initial assessment of the National Youth Gang Suppression and Intervention Program. Due to methodological problems, the scope and seriousness of the youth gang problem are not reliably known. Law enforcement and media reports, however, suggest that criminal youth gangs are active in nearly every State as well as in Puerto Rico and other U.S. territories. The close relationship of gangs, violence, and a significant crime problem are most evident when the criminal records of youth gang members are compared with those of youths who are not in gangs. Youth gang membership is associated with significantly higher levels of delinquency and index crimes. This report considers the characteristics of gang structure, the social contexts in which gangs emerge, emerging and chronic gang problems, and strategic responses. The five basic strategies that have emerged in addressing youth gangs are neighborhood mobilization, social intervention, provision for social and economic opportunities, gang suppression and incarceration, and an organizational development strategy. A discussion of institutional responses focuses on the police, prosecution, the judiciary, probation/parole, corrections, schools, community organizations, and employment. Policies and procedures, as well as promising approaches, are also summarized. Common elements associated with reducing the youth gang problem for significant time periods include clear recognition of a youth gang problem, proactive leadership by representatives of significant criminal justice and community-based agencies, mobilization of both formal and informal community networks, and a focus on community activities that contribute to positive youth development.