The relations between resting heart rate on electrocardiogram, usual physical activity, and risks of all noncardiovascular mortality, cancer mortality, and other noncardiovascular mortality were examined in 7,735 middle-aged British men drawn from general practices in 24 British towns. Subjects were examined and administered questionnaires in 1978-1980. During a follow-up period of 9.5 years (to December 1989), there were 334 deaths from noncardiovascular causes, including 225 cancer deaths. A strong positive association was seen between heart rate and all noncardiovascular mortality, cancer mortality, and other noncardiovascular mortality, even after adjustment for age, blood cholesterol, body mass index, heavy alcohol drinking, physical activity, preexisting ischemic heart disease, smoking, social class, and systolic blood pressure (p < 0.01). The relative risks in men with heart rates of > or = 90 beats/minute, in comparison with those with heart rates of < 60 beats/minute, were 2.33 (95% confidence interval (CI) 1.42-3.74) for total noncardiovascular mortality, 1.68 (95% CI 0.92-3.10) for cancer mortality, and 3.56 (95% CI 1.65-7.65) for mortality due to other noncardiovascular causes. The positive associations with cancer and all noncardiovascular mortality persisted even after further adjustment for lung function (forced expiratory volume in 1 second) and exclusion of men with underlying ill health and of deaths occurring within the first 5 years of follow-up. A significant inverse association with seen between physical activity and risk of cancer death, even after adjustment for the above factors and heart rate, with a significant reduction only in those engaged in high levels of usual physical activity (relative risk = 0.62, 95% CI 0.39-0.98). The data suggest that in middle-aged men, resting heart rate and physical activity are independent prognostic factors for cancer mortality.