The AIDS dementia complex (ADC) is a frequent complication of advanced HIV infection. In order to better define the neuropsychological character and progression of the ADC, four groups of subjects were studied with a battery of neuropsychological tests: an HIV-seronegative comparison group (n = 20), asymptomatic HIV-seropositive patients (n = 16), newly diagnosed AIDS patients (n = 44) and AIDS patients who were referred for neurological consultation (n = 40). Results showed significant reductions in performance in the two AIDS groups, with impairment being most prominent in tests that assessed motor speed and fine control, concentration, problem solving and visuospatial performance. This pattern of neuropsychological dysfunction is consistent with the characterization of the ADC as a subcortical dementia.