The objective of this article is to describe the methods of assessing cardiovascular conditions among older adults recruited to the Cardiovascular Health Study (CHS), a cohort study of risk factors for coronary disease and stroke. Medicare eligibility lists from four US communities were used to obtain a representative sample of 5201 community-dwelling elderly, who answered standardized questionnaires and underwent an extensive clinic examination at baseline. For each cardiovascular condition, self-reports were confirmed by components of the baseline examination or, if necessary, by a validation protocol that included either the review of medical records or surveys of treating physicians. Potential underreporting of a condition was detected either by the review of medical records at baseline for other self-reported conditions or, during prospective follow-up, by the investigation of potential incident events. For myocardial infarction, 75.5% of the self-reports in men and 60.6% in women were confirmed. Self-reported congestive heart failure was confirmed in 73.3% of men and 76.6% of women; stroke, in 59.6% of men and 53.8% of women; and transient ischemic attack, in 41.5% of men and 37.0% of women. Underreporting was also common. During prospective follow-up of an average of about 3 years per person, approximately 50% of men and 38% of women were hospitalized or investigated for at least one potential incident event; for each cardiovascular condition, about 1 to 4% of those investigated during prospective follow-up were found to have had the cardiovascular condition prior to entry into the cohort.(ABSTRACT TRUNCATED AT 250 WORDS)