OBJECTIVE: Chronic mentally ill adults have been found to be at risk for HIV infection. The authors investigated the prevalence of HIV risk behaviors among psychiatric outpatients. Correlates of HIV risk factors and characteristics of patient relationships in which risk occurred were investigated. METHOD: Structured interviews were conducted with 95 chronic mentally ill adults from urban community support service programs. The interviews focused on sexual and substance use behavior, history of HIV risk behaviors, and relationship characteristics related to risk. RESULTS: The study showed that 27% of all patients had had two or more sex partners in the previous year and 18% had received money or drugs for sex. High rates of illicit drug use were also found, with frequent use of drugs or alcohol in association with sexual activity. Multiple regression analyses showed that use of illicit drugs, meeting sex partners in psychiatric clinics, and meeting partners in bars accounted for a substantial proportion of the variance in HIV risk behavior. CONCLUSIONS: These results suggest an urgent need for HIV prevention programs targeted at urban chronic mentally ill adults. Risk- producing characteristics of patient relationships and social networks should be addressed in the development of prevention interventions.