Background: Youth violence and related aggressive behaviors have become serious public health issues with physical, economic, social, and psychological impacts and consequences. This study identified and evaluated the characteristics of successful school-based violence prevention programs. Methods: Twenty-six randomized controlled trial (RCT), school-based studies that were designed to reduce externalizing, aggressive, and violent behavior between the 1st and 11th grades were analyzed for assessing the effects of 5 program characteristics by comparing results of intervention groups to control groups (no intervention) after intervention using a meta-analysis. Electronic databases and bibliographies were systematically searched, and a standardized mean difference was used for analysis. Results: There was no significant difference between interventions, although programs that used non-theory-based interventions, focused on at-risk and older children, and employed intervention specialists had slightly stronger effects in reducing aggression and violence. Interventions using a single approach had a mild positive effect on decreasing aggressive and violent behavior (effect size = -0.15, 95% CI = -0.29 to -0.02, p =.03). Conclusions: Unlike previous individual study findings, this meta-analysis did not find any differential effects for 4 of the 5 program characteristics. In addition, the significant effect noted was contrary to expectation, exemplifying the complexity of identifying effective program strategies. This study adds to the current literature by assessing the program characteristics of RCT studies in an effort to determine what factors may affect school-based violence prevention program success. © 2008, American School Health Association.