Adolescents who join gangs are more frequently involved in serious delinquency com-pared with those who do not, yet few studies have conducted a prospective examination of risk factors for gang membership. The present study uses longitudinal data to predict gang membership in adolescence from factors measured in childhood Data were from the Seattle Social Development Project, an ethnically diverse, gender-balanced sample (n- 808) followed prospectively from age 10 to 18. Logistic regression was used to identify risk factors at ages 10 through 12 predictive of joining a gang between the ages of 13 and 18. Neighborhood, family, school, peer, and individual factors significantly predicted joining a gang in adolescence. Youth exposed to multiple factors were much more likely to join a gang. Implications for the development of gang prevention interventions are discussed.