Findings show that guns were equated with self-protection, the most prevalent reason given for possession and carrying behaviors of peers. Most youth reported multiple types of involvement in gun-related behaviors and were deeply enmeshed in networks of peers who, from their perspective, were also deeply involved in gun-related behaviors and other crimes. Co-offending in violent events appears to be situational as particular features of the situation are more likely to result in the co-participation of peers in violent events. This study adds to the existent knowledge on the peer contexts of violent delinquency and offers insights to the study of co-offending, particularly with regard to gun violence. The peer context, like the neighborhood environment, shapes the cognitive landscape of urban adolescents in particular ways. With cross-sectional data, the direction of influence of peers on gun-related behaviors was unable to be distinguished. The process by which peers became engaged in violence as co-offenders in particular events can clearly be documented. Data were collected from interviews with 416 violent male offenders from 2 disadvantaged New York City neighborhoods. Tables and references