This study examined the influence of witnessing violence, peer provocation, family support, and parenting practices (monitoring and discipline) on aggression. Participants were 1,196 ninth graders at nine schools in poor, predominantly agricultural, rural communities who completed measures of these variables. Witnessing violence, peer provocation, low levels of family support, and poor parenting practices were each related to higher frequencies of aggression. Witnessing violence and peer provocation partially mediated relations between parenting and aggression, such that students who reported high levels of appropriate parenting reported lower levels of witnessing violence and peer provocation. These were, in turn, related to lower levels of aggression. The relation between family support and aggression was also mediated by peer provocation, though the degree of mediation was not as strong as for parenting. Both parenting and family support moderated the relation between witnessing violence and aggression such that this relation was stronger among adolescents who reported low family support or high levels of poor parenting. Neither parenting nor family support moderated the relation between peer provocation and aggression. Overall, parenting practices had a stronger influence on aggression than did family support. Results were generally consistent across gender. These findings have important implications for intervention efforts.