The centralized case index of the Mayo Clinic and the Rochester Epidemiology Program Project were used to identify any Rochester resident with a diagnosis between 1950 and 1987 of any condition suggesting that coronary heart disease might be present. Included were diagnoses of coronary heart disease, myocardial infarction, angina pectoris, coronary insufficiency, or arrhythmias. All relevant index codes were specified and a computer generated list was provided of the unit record numbers of all candidate cases. The medical histories were then retrieved and reviewed for inclusion. The screened histories were assigned to nurse abstractors whose duty it was to identify from the screening list those patients who satisfied the diagnostic criteria in the protocol as well as the incidence and residence requirements. In case finding of coronary heart disease incidence, the following had to be true: the diagnosis of angina pectoris, myocardial infarction or sudden unexpected death must have satisfied the protocol's diagnostic criteria; the diagnosis must have been a first diagnosis; the patient, at the time of first diagnosis, must have been free of diagnoses of congestive heart failure and valvular heart disease; the patient must have been a resident of Rochester at the time of diagnosis. If all of these criteria were met, the electrocardiograms were read by a physician for case verification. A precoded abstract of the history was prepared for each incidence case. The abstract included: identification and demographic data; information on smoking, hypertension, hypertension therapy, lipids, and use of estrogens; diagnostic factors such as ECG, treatment tests, angiography, and selected laboratory test results. The first myocardial infarction following the first coronary heart disease diagnosis was coded; if the first manifestation of coronary heart disease was a myocardial infarction, the second myocardial infarction was coded to provide a basis for determining reinfarction rates. In the earlier study done from 1950-1969, little data on treatment were abstracted. From 1970 to 1991t, drugs and surgery were abstracted. All death certificates for Rochester and Olmsted County residents for the period 1960-1979 were recoded to the 8th revision of the ICDA in order to obtain comparability over the study period. All deaths suspected of being due to some form of coronary heart disease were reviewed by a group of cardiologists using a clinical classification of death. The cardiologists used medical, hospital, and autopsy records to determine cause of death. Follow up was 99 percent complete. Date of last follow-up and cause of death were recorded.