Prior research has demonstrated that both adolescent gang affiliation and perceived delinquent peer association are important predictors of individual offending. A crucial question is whether and how youth gang affiliation contributes to a spectrum of criminal acts above and beyond the influence of associating with delinquent peers. Using 14 waves of data from the Rochester Youth Developmental Study, an ongoing longitudinal panel study aimed at understanding the causes and consequences of delinquency and drug use in an urban sample of adolescents, the current study employs a relatively new modeling technique—dual trajectory analysis—to illustrate the dynamic relationship between these two measures among 666 male youth. The results suggest that the two measures, while overlapping, may constitute distinct concepts that operate in different ways. The most convincing evidence of gang effects, above and beyond the influence of perceived peer delinquency, is for violent behavior and by extension police arrest. Our findings contribute to developmental research and provide information that informs future gang control efforts.