Morbidity Surveillance: All discharges from the seven-county area hospitals with acute and chronic myocardial heart disease and stroke listed among the discharge diagnoses were recorded using Professional Standards Review Organization data tapes. A ten percent random sample of all recorded diagnoses were validated yearly by abstracting data from hospital records. Each year's validation sample of definite and probable cases of myocardial infarction and stroke formed a cohort to be followed for mortality for one year after the onset of the disease event. Individual hospitals and the Professional Standards Review Organization in the area provided data on the total numbers of coronary care unit admissions and coronary artery bypass operations for each year. Beginning in August 1988, a registry was established for all new incident cases of coronary heart disease at the University of Minnesota Hospital and the Ramsey County Hospital. In 1989, twelve hospitals were part of the myocardial infarction registry.