Demographic and clinical data were recorded for 324 patients who visited an AIDS-related psychiatric outpatient clinic over a three-year period. Seventy-five percent of the patients had a diagnosis of AIDS, AIDS-related complex, or asymptomatic HIV seropositivity. Intravenous drug use and heterosexual relations were the most common HIV transmission risk factors. Seventy-three percent of the patients were black or Hispanic; 51 percent were female. In all stages of HIV infection, adjustment disorder was the most common diagnosis; one third to one half of the patients had substance abuse diagnoses. Only 5 percent were diagnosed with dementia, with the incidence highest (12 percent) in patients with AIDS. On the basis of their experience with the clinic, the authors discuss issues that have proved important in the treatment of patients with the triple diagnoses of medical illness, mental illness, and substance abuse.