Since the mid-l950's, major prospective epidemiological studies in large living population groups have shown unequivocal relationships between several traits and habits (singly and in combination) and the risk of premature clinical atherosclerotic coronary heart disease ( CHD) .1-20 The findings of our group in a sizeable cohort of men originally aged 40 to 59, employed by the Peoples Gas, Light and Coke Company in Chicago, are representative.' Of the 1,594 male employees in this age group on January 1, 1958, 1,465 were examined for the first time for the purposes of this study in 1958. Of these 1,465 men, 1,329 were free of evidence of definite clinical coronary heart disease, were followed without loss over the subsequent years, and underwent no systeinatic intervention by the research group. Data on the relationship between the major coronary risk factors and mortality from new coronary heart disease and from all causes (for the eight-year period 1958-66) are presented in TABLES 1 through 6. The men with frankly elevated serum cholesterol levels in 1958 had subsequent death rates from coronary heart disease and from all causes significantly higher than the men with levels less than 250 mg/100 ml had (TABLE 1). Similarly, men with elevated blood pressures had markedly elevated mortality rates, as 'did cigarette smokers (TABLES 2 and 3). These findings are typical of those reported by others. Correspondingly, overweight was found to be associated with increased risk of dying, at least among nonsmokers (TABLE 4), and the cumulative impact of combined risk factors is well illustrated by TABLES 5 and 6. Diabetes (symptomatic or asymptomatic) is another major coronary risk factor, as is an habitual diet high in calories, total fat, saturated fat, cholesterol, total carbohydrate, refined carbohydrate, sugar, and salt. Physical inactivity, tension-generating personality-behavior patterns, and a family history of premature vascular disease are also important, as are "silent" abnormalities in the resting, exercise, and postexercise electrocardiogram.As indicated, significant evidence on the role of several risk factors was already available by the mid-1950's. In 1957, therefore, our research group