Several imperatives drive the need to establish the merit of treating isolated systolic hypertension in the elderly. These include its higher prevalence with age, the associated excess cardiovascular risks, and the rapid aging of the population. The Systolic Hypertension in the Elderly Program demonstrated a significant reduction in stroke incidence (fatal and nonfatal) (36%, equivalent to preventing 30 strokes per 1,000 participants per 5 years). A 27% reduction in coronary heart disease incidence and a 32% reduction in all major cardiovascular events were also achieved (equivalent to the prevention of 16 and 55 events per 1,000 participants per 5 years, respectively). These results were associated with a treatment regimen in which the primary agent was low-dose chlorthalidone. The benefits accrued to all subgroups identified based on baseline age, race and sex, blood pressure, serum cholesterol levels, and electrocardiographic abnormalities. The reduction in coronary disease is consistent with predictions based on prospective epidemiological studies and is concordant with other recent intervention trials. It is a reasonable inference from the Systolic Hypertension in the Elderly Program findings that middle-aged as well as older people with isolated systolic hypertension, and people with less severe degrees of this condition, particularly when other risk factors are present, would benefit from such therapy. Another reasonable implication of the trial relates to the matter of preferred drug treatment regimens for diastolic hypertension, in middle-aged as well as older people.(ABSTRACT TRUNCATED AT 250 WORDS)