The study was conducted using morbidity and mortality data collected by the Pawtucket Heart Health Program between 1980 and 1993, and risk factor data obtained through biennial cross-sectional household health surveys conducted in random samples of residents in the two study communities. Morbidity and mortality data were obtained according to standardized epidemiologic surveillance methods. Hospitalized cases of coronary heart disease and stroke were identified through hospital discharge records and were validated using a standardized diagnostic algorithm based on data abstracted from medical records. Out-of-hospital deaths identified through death certificate data were validated using an algorithm based upon medical history data and information concerning the circumstances of death obtained from informant interviews.