Classification of the severity of hypertension and recommendations on the blood pressure values to be achieved during antihypertensive drug treatment have for decades been based on diastolic values. It is now clear, however, that systolic blood pressure is by no means less important. This paper will focus on the following sets of evidence: (1) that epidemiologically a selective elevation of systolic blood pressure has a major prevalence in the elderly population; (2) that isolated systolic hypertension carries a marked increase in the risk of cardiovascular disease and that even in systo-diastolic hypertension this risk may be more closely related to systolic than to diastolic blood pressure; (3) that treatment of systolic hypertension greatly reduces cardiovascular complications and that in all conditions this reduction is related to the treatment-induced reduction in systolic blood pressure to a degree similar to or superior to the relationship with the reduction in diastolic blood pressure; and (4) that in the hypertensive fraction of the population, control of systolic blood pressure is achieved much less often than control of diastolic blood pressure. That this last point is also the case in major intervention trials suggests that normalization of systolic blood pressure may be intrinsically more difficult than normalization of diastolic blood pressure, possibly because of the difficulty of reversing the pathophysiological abnormalities responsible for the elevation of systolic blood pressure. This emphasizes the importance of research into new drugs or treatment types with greater efficacy in systolic hypertension.