Conflicting data have been reported regarding the association between occupation and coronary heart disease. We evaluated data on a series of 568 married men who died of coronary heart disease and an equal number of controls matched for age, sex, and neighborhood of residence. Information was collected from the wives of both cases and controls on a larger number of variables, including usual occupation, job-related and leisure-time physical activity, medical history, and life-style. Usual occupation was dichotomized into blue-collar and white-collar work according to the Edwards' classification. White-collar workers had a statistically significant 30% decreased risk of fatal coronary heart disease compared with blue-collar workers once the effects of reported coronary risk factors were considered (relative risk, 0.70; 95% confidence limits, 0.5 to 0.96). These data suggest that occupation is significantly associated with fatal coronary heart disease, and that this increased risk is not explained by a large number of known coronary risk factors. It still remains unclear, however, whether other uncontrolled variables explain the observed association.