Astin's (1977, 1991, 1993) input-environment-outcome (I-E-O) model provided a conceptual framework for this study which measured 156 male college students' willingness to prevent rape (outcome variable). Predictor variables included personal attitudes (input variable), perceptions of close friends' attitudes toward rape and rape prevention (environment variable), as well as exposure to sexual assault peer educators (environment variable). A hierarchical multiple regression analysis revealed that both input and environment variables significantly influenced male college students' willingness to prevent rape. Results from this study may help campus leaders develop programs and practices that engage men in rape prevention, which may subsequently reduce incidents of sexual violence on their campuses. (Contains 2 tables.)