OBJECTIVES: This study examined the prevalence and correlates of violent behavior by individuals with severe mental illness. METHODS: Participants (N = 802) were adults with psychotic or major mood disorders receiving inpatient or outpatient services in public mental health systems in 4 states. RESULTS: The 1-year prevalence of serious assaultive behavior was 13%. Three variables-past violent victimization, violence in the surrounding environment, and substance abuse-showed a cumulative association with risk of violent behavior. CONCLUSIONS: Violence among individuals with severe mental illness is related to multiple variables with compounded effects over the life span. Interventions to reduce the risk of violence need to be targeted to specific subgroups with different clusters of problems related to violent behavior.