A dating violence and sexual assault prevention program was presented to 396, predominately African American, middle schoolers in two inner city schools in the United States. In one school the program was offered with a same-gender group composition; in the other school, the same program was offered with mixed-gender group composition. A quasi-experimental design was used to assess how gender composition in programming influenced youths' attitudes about dating violence. Study findings suggest that boys benefit most from participation in a same-gender program and girls benefit most from a mixed-gender program. Implications for prevention programming are discussed. (Contains 2 tables.)