BACKGROUND AND PURPOSE: Infarctlike lesions are frequently detected in symptomatic and asymptomatic older persons undergoing cerebral MRI, but their significance in older adults has not been examined. We determined the prevalence of MRI infarcts in a population-based sample of men and women aged > or = 65 years and related these findings to demographic, cognitive, and neurological status. METHODS: MRI scanning was performed in 3660 Cardiovascular Health Study (CHS) participants after brief neurological examinations and tests of cognitive function. MRIs were read centrally for the presence of an infarct > or = 3 mm in diameter or smaller infarctlike lesions. RESULTS: MRI infarcts were detected in 1131 of 3647 participants with readable infarct information (31%) and in 961 of the subgroup of 3397 participants (28%) without known prior stroke ("silent" MRI infarcts). Smaller infarctlike lesions were found in 196 of 2516 participants who had no MRI infarcts > or = 3 mm. MRI infarcts were more common in participants who were older, had prior stroke, impaired cognition, visual field deficits, slowed repetitive finger tapping (all P < .0001), weakness on toe and heel walking, and history of memory loss, coma, or migraine headaches. Multivariate analysis in those without prior stroke showed strong associations of silent MRI infarcts with older age, history of migraines, lower digit symbol scores, and more abnormalities on neurological examination. CONCLUSIONS: MRI evidence of brain infarction is common in older men and women without a clinical history of stroke. Their strong associations with impaired cognition and neurological deficits suggest that they are neither silent nor innocuous.