Infection with the human immunodeficiency virus frequently results in a dementing illness which manifests predominantly as a subcortical dementia. Parkinsonian features may be prominent in these patients and may on occasion be the presenting manifestation. These patients are exquisitely sensitive to dopaminergic blocking agents. Radiological studies, metabolic uptake studies and pathological examination of the brain suggest that the basal ganglia are the major target of this infection. Although further studies are necessary to determine appropriate treatment for this condition and to develop an understanding of the underlying pathophysiological mechanisms, available evidence suggests that the response to dopamine agonists may be variable and that viral strains and viral products may specifically target cells within the basal ganglia.