The growing population of chronically mentally ill persons who are HIV-positive or who have AIDS has not yet been adequately studied. We describe the entire population of known HIV-positive inpatients in a state psychiatric center in New York City. In this sample, the typical patient with known HIV infection is as likely to be a man as a woman and is a member of an ethnic minority group. HIV-positive patients had multiple risks for HIV infection including injecting drug use (IDU), sex with IDU partners, prostitution and male homosexual activity. Most patients were at a late stage of HIV-infection, typically with CD4+ cell counts of 400. Discharge plans were complicated by HIV illness and most HIV-positive patients had a longer length of hospital stay than non HIV-positive patients. We discuss the need to plan for the management of increasing numbers of HIV-positive patients in inpatient, outpatient, and residential facilities.