Data on the relationship between Parkinson's disease (PD) and stroke have been conflicting, some studies showing a reduced risk of stroke during life, and others indicating an increased risk of stroke-related death. Consecutive cases (n=617) of autopsy-proven idiopathic PD (Lewy body disease of the brain stem type) and age-matched controls (n=535) were compared using current routine and immunohistochemical methods. The total frequency of cerebrovascular lesions (lacunes, amyloid angiopathy, white matter lesions, old and recent ischemic infarcts and hemorrhages) in PD (44.0%) was higher than in controls (32.8%), while acute, often fatal ischemic or hemorrhagic strokes were less frequent in parkinsonian patients (1.8% vs 2.6%). Like previous postmortem findings in a smaller cohort, these findings neither indicate a protective effect against stroke nor a greater susceptibility to death from stroke in the populations studied. Cognitive impairment in PD appears to be largely independent from coexistent vascular pathology except in cases with severe cerebrovascular lesions.