Thirty-three HIV-positive patients with clinical signs of dementia according to the 1991 AAN criteria underwent psychometric, electrophysiological and radiological examination and were compared with a group of normal healthy subjects and a cohort of clinically asymptomatic HIV-1-positive individuals of comparable education and social environment. Compared with the other groups, test performance was severely impaired in the demented patients. Results of motor testing and MRI revealed that subcortical structures were not exclusively affected, but most severely and early, thus characterizing the clinical feature in HIV-1-associated dementia. In demented patients a rapid deterioration was observed, leading to death within about 12 months on average, which is a markedly shorter survival time than described in the literature for non-demented HIV-1-positive individuals.