This study examined the relationships between prosocial involvement (PI), antisocial peer affiliations (APA), and the degree of their overlapping or independent prediction of behavior problems in urban adolescents. Two dimensions of behavior were assessed at ages 9-11 and at ages 13-15: disruptive, aggressive conduct and number of delinquent behaviors in the past year. Participants were 167 urban boys and girls with multiple early childhood risk factors. APA predicted higher rating of aggressive conduct and more delinquent behaviors at ages 13-15 beyond the effects of earlier behavior problems. PI predicted lower rates of delinquent behavior but not aggressive conduct. A portion of the influence of PI on delinquent behavior was independent and a portion overlapping with APA. High PI moderated the positive relationship between APA and delinquent behavior, consistent with a protective effect. Interventions that promote PI are unlikely to substantially reduce associations with antisocial peers but may prove beneficial for youths with many antisocial friends by reducing contagion effects that promote delinquency. Other implications for prevention efforts are also considered. (Contains 5 tables and 1 figure.)