While youth violence has always been a critical part of delinquency, the modern epidemic is marked by high rates of gun violence. Adolescents in cities possess and carry guns on a large scale, and guns play a central role in initiating, sustaining, and elevating the epidemic of youth violence. The demand for guns among youth is fueled by an "ecology of danger," comprising street gangs and expanding drug markets with high intrinsic levels of violence, high rates of adult violence and fatalities, and cultural styles of gun possession and carrying. Guns have become symbols of respect, power, identity, and manhood to a generation of youth, in addition to having strategic value for survival. The effects of guns are mediated by structural factors that increase the youth demand for guns, the available supply, and culture and scripts that teach youngsters lethal ways to use guns. The article includes characteristics and risk factors for adolescent gun possession, several explanations of adolescent gun violence and gun homicide rates, establishment and maintenance of identity through lethal violence, and research and intervention on adolescent gun violence. Notes, references