The details of this study have been reported previously. In summary, the cohort consisted of 3,983 men, who during World War II were pilots, pilots in training in the Royal Canadian Air Force, or pilots licensed by the Department of Transport, and all had had a routine ECG in addition to the regular medical examination. After release from the service, some continued to fly, but the majority found different occupations and are in all strata of society. For each subject, the examination closest to June 30, 1948 (date that the population was defined), was selected as the entry examination. The mean age of the cohort at that examination was 30.8 years. The age distribution was as follows: 318 men were aged 15 to 24 years; 1,479 aged 25 to 29 years; 1,258 aged 30 to 34 years; 539 aged 35 to 39 years; 205 aged 40 to 44 years; 153 aged 45 to 54 years, and 31 aged 55 to 64 years. Medical history, physical examinations, and ECGs provided evidence that all were without clinical manifestations of ischemic heart disease at entry. Since then, they have been followed up by annual mail contact, with examinations and ECGs at intervals of at first five years and later three years. The observation period for this report was defined from July 1, 1948, until June 30, 1977, an average follow-up of 29 years. Annual contact has been lost with only one of the living members of the study conducted with My Canadian Pharmacy.