The aim of this study was to establish the prevalence of current and past psychiatric morbidity in HIV seropositive asymptomatic subjects belonging to three transmission categories (gay men, intravenous drug users, and heterosexuals) compared with that found in HIV seronegative controls from the same groups. A cross-sectional, controlled study including 279 seropositive subjects belonging to groups II and III defined by the Center for Disease Control (94 gay men, 157 intravenous drug users, and 28 heterosexuals) and 159 seronegative subjects (38 gay men, 91 intravenous drug users, and 30 heterosexuals) is reported. Outcome measures included standardised, self-report questionnaires and a semistructured interview to assess current psychopathological status and past psychiatric history. In addition, a psychiatric diagnosis according to DSM-III-R criteria Axis I and II was made in the seropositive subjects. Results showed that these subjects differed very little from the controls and that overall levels of psychiatric disturbances in both groups were low and similar to those found in other life-threatening illnesses. Furthermore, intravenous drug users, regardless of HIV serological status, had the highest levels of psychological morbidity. Psychosocial distress was associated with previous and current lifestyle, independently of HIV status.