BACKGROUND: Regular exercise has been associated in prospective studies with reduced incidence of cardiovascular disease (CVD) and death. OBJECTIVE: To assess in a cohort study whether there is a similar protective effect of regular exercise among hypertensive individuals. DESIGN: Population-based prospective cohort study. Spare time physical activity was assessed by structured interview. SETTING: Malmo, Sweden. PARTICIPANTS: Healthy men (n = 642) born in 1914. A baseline examination took place in 1969-1970. MAIN OUTCOME MEASURES: All-cause and cardiovascular mortality rates during 25 years of follow-up in relation to blood pressure and other risk factors for atherosclerosis. RESULTS: One-hundred (16%) men reported vigorous spare time physical activity. In this group, 31 had hypertension (blood pressure >160/95 mm Hg or treatment for hypertension), 47 were smokers and 39 had hyperlipidaemia. Among the 173 men with hypertension, vigorous physical activity was associated with markedly reduced rates of all-cause (17.3 versus 40.0 deaths per 1000 person-years) and cardiovascular mortality (6.3 versus 21.0 deaths per 1000 person-years). The risk reductions associated with exercise remained statistically significant after adjustment for smoking, systolic blood pressure and antihypertensive therapy. The relative risk was 0.43 (confidence interval 0.22-0.82) for total mortality and 0.33 (confidence interval 0.11 -0.94) for CVD mortality. CONCLUSION: People who regularly perform physical activity constitute a heterogeneous group with regard to their exposure to known cardiovascular risk factors. Our results support the view that regular physical activity is associated with a reduced incidence of cardiovascular disease and death and suggest that this protective effect may be enhanced among hypertensive individuals.