Developmental patterns of childhood peer relations were examined in the prediction of externalizing behavior problems in a 4-year multiple cohort longitudinal study. The participants consisted of 880 third- (M = 9.3 years) through seventh- (M = 13.4 years) grade students. Approximately half of the participants were female, one third were Black, and one third were from low-income homes. Developmental patterns of six indices of peer relations (including group acceptance, group rejection, having a reciprocated best friend, social support from best friend, conflict with best friend, and the aggressiveness of the best friend) were examined as predictors of aggression and delinquency using logistic regression analyses. Results suggest that both group and dyadic peer relations problems are risk factors for aggression and delinquency. Support was found for the cumulative risk model in the prediction of externalizing outcomes from multiple social risk factors that were additively associated with each negative outcome.