The study was based on data including risk factors and autopsy brain sections from deceased men from the Honolulu Heart Program. In this cohort, medial and intimal lesions of brain parenchymal arteries were significantly associated with brain infarction and three times more common in men dying of stroke than of non-cardiovascular causes. The specific aims of the study were 1) delineation of the morphologic characteristics of the brain parenchymal artery lesions, their regional anatomic distribution, and their relationship to changes in adjacent brain parenchyma and the degree of atherosclerosis in the major intracranial arteries; 2) characterization of the relationship in men between the arterial lesions and advancing age; 3) characterization in men over 60-65 years of age of the relationship of the arterial lesions to stroke, brain infarction or hemorrhage, and dementia; 4) identification of additional risk factors associated with the arterial lesions. The arterial lesions and adjacent brain parenchyma were examined with conventional histologic stains and immunohistochemical markers for specific cellular and extracellular components of the arterial wall. The prevalence and extent of each type of arterial lesion were determined at three anatomic sites. Baseline risk factors thought to be related to stroke and brain infarction were examined for association with the arterial lesions. Statistical tests of association were based on univariate and multivariate linear and logistic regression models controlled, when necessary, for age.