The AIDS patient population in the United States is distinctly different from the general population in ethnic and racial composition. While Blacks and Hispanics represent 12 percent and 6 percent, respectively, of the 1980 U.S. population, they constitute 26 percent and 15 percent, respectively, of AIDS patients as of October 1988. The over-representation of Blacks and Hispanics among AIDS patients is related to the high incidence of AIDS cases within these groups that are associated with intravenous drug use. Neuropsychiatric manifestations of AIDS include an AIDS dementia complex, central nervous system dysfunction, and acute psychosis. Patients who are severely disturbed and psychotic may present to State hospitals with HIV encephalopathy. In chronically and severely ill patients, physical symptoms that include oral and cutaneous conditions, the HIV wasting syndrome, and lymphadenopathy may provide early clues to HIV infection. In general, populations served by State psychiatric facilities may be a greater risk for exposure to HIV infection and may be less likely to give adequate histories of AIDS-related risk behaviors or previous medical illness. Early neuropsychiatric and medical findings in HIV infection are discussed, and a clinical case is presented. 33 references.