This study reports the findings of a multisite randomized trial evaluating the separate and combined effects of 2 school-based approaches to reduce violence among early adolescents. A total of 37 schools at 4 sites were randomized to 4 conditions: (1) a universal intervention that involved implementing a student curriculum and teacher training with 6th-grade students and teachers, (2) a selective intervention in which a family intervention was implemented with a subset of 6th-grade students exhibiting high levels of aggression and social influence, (3) a combined intervention condition, and (4) a no-intervention control condition. Analyses of multiple waves of data from 2 cohorts of students at each school (N = 5,581) within the grade targeted by the interventions revealed a complex pattern. There was some evidence to suggest that the universal intervention was associated with increases in aggression and reductions in victimization; however, these effects were moderated by preintervention risk. In contrast, the selective intervention was associated with decreases in aggression but no changes in victimization. These findings have important implications for efforts to develop effective violence prevention programs. (Contains 7 tables, 2 figures, and 7 footnotes.)