An analysis of the prevalence and patterns of youth violence notes that violence touches the lives of nearly every child and adolescent; that youth violence has deep roots in United States society; and that youth violence imposes significant individual, social, and economic costs. Self-reported violent behavior has been relatively stable during the past two decades, but the number of youths who carry weapons and display aggressive behaviors remains unacceptably high. Recent decreases in violence are promising, but they have been inconsistent across youth subgroups. Survey data also reveal that youths are often the victims of violence. Additional chapters examine biological, psychological, social, and environmental factors related to violence and review strategies and instruments for assessing aggressive and violent tendencies in children and youths; innovative prevention treatment strategies in the context of victimization and gender and in the social environments of schools and communities. Further chapters trace the relationship between childhood victimization and involvement in violent conduct during adolescence, violent behavior in female juveniles, and school violence and approaches to school safety. Other chapters focus on the relationship between juvenile drug use and violence and discuss risk factors for serious juvenile delinquency and gang violence, recent trends in gang membership, and clinical issues associated with assessing and treating gang members. The final chapter offers policy recommendations for addressing structural factors related to the onset and maintenance of youth violence. Figures, tables, index, and chapter reference lists