Persons with severe mental illness (SMI) are disproportionately affected by HIV/AIDS. This study examined multivariate correlates of sexual risk among 152 adults with SMI receiving outpatient psychiatric treatment. Structured interviews assessed psychiatric, psychosocial, and behavioral risk factors. The majority was sexually active (65%), and many reported unprotected intercourse (73%), multiple partners (45%), and sex trading (21%) in the past year. Logistic regression models found that sexual behaviors were differentially associated with non-psychotic disorder, psychiatric symptoms, substance abuse, childhood sexual abuse, romantic partnership, and social support (all ps < .05). Findings underscore the need for targeted HIV prevention interventions that address psychiatric and psychosocial risk factors.