The prevalence of childhood sexual and physical abuse among persons with severe mental illness (SMI) is disproportionately high. Adults with SMI also engage in high rates of HIV risk behaviors. This study examined the association between childhood abuse and adult victimization, substance abuse, and lifetime HIV sexual risk in a sample of 152 adults with SMI receiving community mental health services. Structured interviews assessed psychiatric, psychosocial, and behavioral risk factors. Seventy percent reported childhood physical and/or sexual abuse, and 32% reported both types of abuse. Participants with childhood abuse were more likely to report adult victimization and greater HIV risk. A structural equation model found that childhood abuse was directly and indirectly associated with HIV risk through drug abuse and adult vicitimization. Integrated treatment approaches that address interpersonal violence and substance abuse may be necessary for HIV risk reduction in this population.