The Cardiovascular Health Study (CHS) is a longitudinal population-based study of coronary heart disease and stroke in men and women 65 years and older. The initial CHS cohort consisted of 5201 men and women recruited from a random sample of the Health Care Financing Administration (HCFA) Medicare eligibility lists in four communities in the United States. Extensive historical, physical, and laboratory evaluations were performed at the baseline examination in 1989 to 1990 to identify risk factors and subclinical disease. Periodic contacts are carried out to ascertain and verify incident cardiac and stroke events and their sequelae. Since only a short time has passed since entry of all the patients into the study, data are not available on time trends in the mortality rate of stroke, but we expect to contribute in this area in the years ahead. This article then is a description of the CHS, of methods of assessing stroke in the CHS cohort, and of prevalence of stroke and transient ischemic attacks at the initial examination.