OBJECTIVES: This study assessed the effects of the Safe Dates program on the primary and secondary prevention of adolescent dating violence. METHODS: Fourteen schools were randomly allocated to treatment conditions. Eighty percent (n=1886) of the eighth and ninth graders in a rural county completed baseline questionnaires, and 1700 (90%) completed follow-up questionnaires. RESULTS: Treatment and control groups were comparable at baseline. In the full sample at follow-up, less psychological abuse, sexual violence, and violence perpetrated against the current dating partner were reported in treatment than in control schools. In a subsample of adolescents reporting no dating violence at baseline (a primary prevention subsample), there was less initiation of psychological abuse in treatment than in control schools. In a subsample of adolescents reporting dating violence at baseline (a secondary prevention subsample), there was less psychological abuse and sexual violence perpetration reported at follow-up in treatment than in control schools. Most program effects were explained by changes in dating violence norms, gender stereotyping, and awareness of services. CONCLUSIONS: The Safe Dates program shows promise for preventing dating violence among adolescents.