The relationship between grade of employment, coronary risk factors, and coronary heart disease (CHD) mortality has been investigated in a longitudinal study of 17 530 civil servants working in London. After seven and a half years of follow-up there was a clear inverse relationship between grade of employment and CHD mortality. Men in the lowest grade (messengers) had 3.6 times the CHD mortality of men in the highest employment grade (administrators). Men in the lower employment grades were shorter, heavier for their height, had higher blood pressure, higher plasma glucose, smoked more, and reported less leisure-time physical activity than men in the higher grades. Yet when allowance was made for the influence on mortality of all of these factors plus plasma cholesterol, the inverse association between grade of employment and CHD mortality was still strong. It is concluded that the higher CHD mortality experienced by working class men, which is present also in national statistics, can be only partly explained by the established coronary risk factors.