RTI International is helping to expand and advance the scientific knowledge base of violence prevention by rigorously evaluating prevention strategies, programs, and policies to address specific gaps in the prevention of teen dating violence, intimate partner violence, sexual violence, and youth violence. Men Can Stop Rape (MCSR) is a non-profit community-based violence prevention organization that has developed a theoretically-based 22-week curriculum that is delivered in high schools as an after school program called Men of Strength (MOST) Club. RTI is working with MCSR to rigorously evaluate the impact of the MOST Club curriculum on perpetration of physical and sexual violence and on bystander behavior. Additionally, the MOST Club curriculum is unique as its primary mechanism of change is to shift the narrative of masculinity among high school men who can serve as peer leaders. Combining a traditional randomized control trial based evaluation with social network referrals will allow examination of program effects on both Club participants and male and female peers with whom participants regularly come in contact.