A large study of 7718 men aged 40 to 59 years, randomly selected in 24 British cities, in order to determine risk factors for coronary heart disease. Of 7718 men who provided information about smoking, 5899 (76.4%) smoked a certain period of life (including those who smoke now and who smoked in the past). For 10 years, 650 of the 7718 men (8.4%), myocardial infarction. What design of the study was conducted

-cohort study