Results show that the intervention appeared to reduce self-reported peer violence victimization and self-reported perpetration on some of the measures in these areas, though there was a conflicting finding regarding self-reported dating violence perpetration. The intervention seemed to increase self-reported dating violence perpetration for some of the measures in this area, but not self-reported dating violence victimization. Sexual harassment and gender violence, including interpersonal or dating violence, are serious problems in K-12 schools. Previous research shows that gender violence and harassment (GV/H) can lead to severe injuries for victims, poorer mental or physical health, more high-risk or deviant behavior, and increased school avoidance. Many schools that address GV/H do so by developing and implementing intervention programs. However, little is know about the effectiveness of these interventions. This report provides a detailed account of the results of an experimental evaluation, supported by the U.S. Department of Justice, National Institute of Justice that used a randomized controlled trial of a GV/H prevention program for sixth and seventh grade students in three suburban school districts bordering Cleveland, OH. Approximately 100 sixth and seventh grade classrooms were assigned randomly to either receive 1 of 2 intervention curricula or a true no-treatment control condition. Through student surveys, the study assessed whether GV/H prevention programming reduced the probability of self-reported GV/H perpetration and victimization, had no effect, or led to negative effects. The study also explored the impact of the prevention curricula on student self-reports of attitudes, knowledge, and behavioral intentions as they related to GV/H and sexual harassment. Tables, references, and appendixes A-N