Blood pressure (BP) levels alone have been traditionally used to make treatment decisions in patients with hypertension. The sixth report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI) recently recommended that risk strata, in addition to BP levels, be considered in the treatment of hypertension. We estimated the absolute benefit associated with a 12 mm Hg reduction in systolic BP over 10 years according to the risk stratification system of JNC VI using data from the National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. The number-needed-to-treat to prevent a cardiovascular event/death or a death from all causes was reduced with increasing levels of baseline BP in each of the risk strata. In addition, the number-needed-to-treat was much smaller in persons with > or =1 additional major risk factor for cardiovascular disease (risk group B) and in those with a history of cardiovascular disease or target organ damage (risk group C) than in those without additional major risk factors for cardiovascular disease (risk group A). Specifically, the number-needed-to-treat to prevent a death from all causes in patients with a high-normal BP, stage 1 hypertension, or stage 2 or 3 hypertension was, respectively, 81, 60, and 23 for those in risk group A; 19, 16, and 9 for those in risk group B; and 14, 12, and 9 for those in risk group C. Our analysis indicated that the absolute benefits of antihypertensive therapy depended on BP as well as the presence or absence of additional cardiovascular disease risk factors and the presence or absence of preexisting clinical cardiovascular disease or target organ damage.