The authors randomly assigned school-based interventions to 30 public middle schools in New York City, and identified 117 sixth and seventh grade classes to randomly receive additional classroom interventions. The classroom intervention was a six session curriculum that emphasized the consequences of dating violence and harassment (DV/H), laws and penalties for DV/H, the construction of gender roles, and healthy relationships. The building-based intervention included the use of temporary school-based restraining orders, higher levels of faculty and security presence in areas identified through student mapping of safe/unsafe "hot spots," and the use of posters to increase awareness and reporting of DV/H to school personnel. Quantitative surveys were implemented at baseline, immediately after the intervention, and 6 months post-intervention, and included measures of knowledge, attitudes, behavioral intentions, intentions to intervene as a bystander, peer and dating partner physical and sexual violence, sexual harassment, and other background items. Qualitative focus groups were conducted with interventionists and students to provide rich contextual to assess intervention implementation and student change associated with the interventions. Participating students ranged in age from 10 to 15 with 53 percent being female, 40 percent having prior experience with a violence prevention educational program, 50 percent reporting being in at least one dating relationship, 20 percent reporting having been the victim of dating violence, and 66 percent victims of peer violence. The combination of the classroom and building interventions, and the "building only" intervention led to 32-47 percent lower peer sexual violence victimization and perpetration up to 6 months after the intervention. The success of the "building only" intervention is particularly important because it can be implemented with very few extra costs to schools. Focus groups confirmed that the interventions were implemented as planned, teachers liked and were supportive of the interventions, and the positive survey results related to the interventions effectiveness were confirmed.