We examined the relation between reported regular strenuous exercise or hard physical labor and the incidence of coronary heart disease (CHD) death and nonfatal myocardial infarction among 1,533 hypercholesterolemic men aged 35-59 years who were in the placebo group of the Lipid Research Clinics Coronary Primary Prevention Trial. The mean follow-up of the cohort was 7.4 years. The men were free of clinical heart disease at entry; men with an abnormal resting electrocardiogram or graded exercise test also were excluded. Regular physical activity was not associated with the incidence of CHD (RR = .94, 95% CI = .68, 1.38) in this study population. Adjustment by the proportional hazards model for age, low-density lipoprotein cholesterol, smoking, family history of CHD, and occupation did not alter this finding. This observation suggests that reported regular physical activity may not be related to the risk of coronary heart disease among asymptomatic, hypercholesterolemic, middle-aged men.