Résumé : A sample of 5,262 male post office employees underwent an examination for atherosclerosis. This examination was carried out at two different centers using the same standardized methods. The biological analyses were carried out by the same laboratory. Important differences were observed between the two centers in the prevalence of coronary disease and in the mean cholesterolemia. At first sight, two factors appear to cause, at least partially, these differences: nutritional habits and the degree of sedentariness of the subjects.