The treatment of arterial hypertension is based on results from several large prospective randomized intervention trials that demonstrated significant benefits from antihypertensive therapy in terms of reduced cardiovascular morbidity and mortality, mainly from strokes, but also from myocardial infarction, congestive heart failure and other vascular or renal complications. Nonetheless, it is obvious that such studies, for a number of reasons, underestimate the true benefit of lowering elevated arterial pressure. Active treatment given to patients allocated randomly to be administered placebo is an important factor, particularly since active treatment is given preferentially to the placebo patients with the highest risk. Recruitment of low-risk patients into studies is another reason for the underestimation of benefit. Moreover, significant loss of patients to follow-up plays a role. Two recent epidemiological surveys, in Framingham and Göteborg, showed markedly beneficial blood pressure-related changes in those populations, suggesting that the long-term effects of antihypertensive therapy may in fact have been underestimated by intervention studies