We determined the frequency of dementia in a cohort of 251 patients aged greater than or equal to 60 years hospitalized with acute ischemic stroke, based on examinations performed 3 months after stroke onset. Using modified DSM-III-R criteria, we found dementia in 66 patients (26.3%). Diagnostic agreement among raters was excellent (kappa = 0.96). In a control sample of 249 stroke-free subjects recruited from the community and matched by age, we found dementia in eight subjects (3.2%). Using a logistic regression model to estimate the risk of dementia associated with stroke in the combined samples, the odds ratio (OR) for stroke patients compared with control subjects was 9.4 (p less than 0.001). Advancing age and fewer years of education were significant, independent correlates of dementia, with a trend evident for race (non-white versus white). Confining the analysis to subjects residing in the Washington Heights-Inwood community of northern Manhattan, the OR was 10.3 (p less than 0.001) with significant age and race effects. We conclude that ischemic stroke significantly increases the risk of dementia, with independent contributions by age, education, and race.