Data from an online community sample of young men were analyzed to test predictors of sexual assault perpetration. We used structural equation modeling to test the relative contributions of specific sub-types of childhood adversity to subsequent sexual aggression. Mediators included hostile masculinity, impersonal sexual behavior and attitudes, and substance use variables. Findings suggested that childhood sexual abuse had direct and mediated effects on sexual assault perpetration, but hostile masculinity was the only proximal factor significantly related to aggression. Childhood polytrauma was also associated with increased perpetration risk, suggesting that prevention efforts may be aided by increased attention to childhood maltreatment.