Resting heart rates were ascertained during the 1978-1979 school year in 3590 children aged 5-17 years in the biracial geographic population of Bogalusa, Louisiana. These rates were found to be relatively independent of the method of measurement, whether supine by physician's stethoscope or dressed sitting radial pulse taken by a nurse, and in either case adhering to a strict measurement protocol. Apart from the known influences of age and sex, the authors found a small but consistent racial influence, with whites having 3-4 beats/min higher rates than blacks. Controlling for age, the authors found heart rate to be positively correlated with blood pressure in whites and with subcapsular skinfold thickness in boys. No consistent relation between heart rate and amount of cigarettes smoked was observed. Boys in the upper five percentiles of blood pressure-heart rate ("double") product values were found to have about twice the subscapular skinfold thickness compared to the lower five percentiles. Likewise, boys in the upper five percentiles of subscapular skinfold thickness had significantly increased double products. Since the double product is an index of cardiac oxygen consumption, this finding could point to a possible etiologic link between obesity and chronic cardiac stress in males beyond the mediation of lipoproteins, cholesterol, and diabetes mellitus in contributing to atherosclerotic heart disease, but this issue needs further study. Ascertainment of resting heart rate provides an additional parameter in the study of cardiovascular risk factor variables, in youth as in adulthood, to supplement the natural history of the atherosclerosis-hypertension syndrome with its sequelae.