This paper reviews the theoretical and practical importance of studying contextual factors in school-based violence prevention programs and provides a framework for evaluating factors at the classroom, school, and community/district level. Sixty-two published papers describing 38 different programs were reviewed; of these 16 were identified that reported data on contextual effects or discussed possible contextual effects on the intervention. The small number of studies precludes definitive conclusions regarding contextual effects in school-based violence prevention programs, but suggests (a) some evidence for contextual effects on program outcomes, and (b) interdependence of context and implementation factors in influencing outcomes.Editors' Strategic Implications: This review suggests that contextual effects are important to school violence prevention, as context can influence outcomes directly and through interactions with implementation factors. Consequently, characteristics of the classroom, school, and community contexts should be considered by practitioners when implementing prevention programs and measured by researchers studying the processes and outcomes of these programs.