Previous studies have shown positive associations between heart rate and both all-cause and cardiovascular mortality. These relationships, however, have not been investigated in persons with hypertension. Using 36-year follow-up data from the Framingham Study, we evaluated from 4530 subjects, aged 35 to 74, whose blood pressures were > or = 140 mm Hg systolic or > or = 90 mm Hg diastolic and who were not treated with antihypertensive medication. We used pooled logistic regression to calculate biennial mortality rates. Odds ratios and 95% confidence intervals for each increment in heart rate of 40 beats/min, adjusted for age and systolic blood pressure level, were: for all-cause mortality, 2.18 (1.68, 2.83) for men and 2.14 (1.59, 2.88) for women; and for cardiovascular mortality, 1.68 (1.19, 2.37) for men and 1.70 (1.08, 2.67) for women. Exclusion of outcomes in the first 2 or 4 years after measurement of heart rate did not materially change the results, which suggests that rapid heart is not merely an indicator of preexisting illness. Therefore heart rate may be an independent risk factor for cardiovascular death in persons with hypertension.