A vascular etiology of Parkinson's disease (PD) has been long debated. In order to search for an ischemic basis of PD we assessed the clinical symptomatology of a consecutive group of 60 PD patients and compared their frequency of cerebrovascular risk factors, carotid atherosclerosis and ischemic brain lesions with age-matched groups of stroke patients and normals. There were 16 (27%) subjects with PD who also had symptoms of cerebrovascular disease. The frequencies of carotid stenoses, ischemic brain lesions and most of cerebrovascular risk factors seen in the latter group was comparable with those of stroke patients and significantly higher than in the investigational subsets of patients with "pure" PD and normals. Only one (1.6%) individual with PD presented signs suggestive of an ischemic etiology of parkinsonism. These findings suggest that cerebrovascular disease occurs in approximately one fourth of patients with PD, but seldomly is causally related.