Diastolic hypertension has been widely and justifiably accepted as a cause of cardiovascular mortality. However, it has also been accepted that the cardiovascular sequelae of hypertension derive chiefly from the diastolic component. Because systolic and diastolic pressure are usually highly correlated it is not easy to dissociate the effects of each. Statistical analysis suggests that systolic pressure is actually the more potent contributor to cardiovascular sequelae. Even isolated systolic pressure elevation is associated witn an excess cardiovascular mortality. At low diastolic pressures (i.e., less than 95 mm Hg), risk rises with the level of systolic pressure. Also, isolated systolic hypertension is most ominous in the elderly, in whom it is highly prevalent. Isolated systolic hypertension was related to the occurrence of "direct" complications as well as to atherosclerotic sequelae. It was also associated with excess mortality, taking into account rigid vessels as judged from pulse-wave recordings. Trials to determine whether the treatment of isolated systolic hypertension is efficacious for avoiding its demonstrated excess cardiovascular morbidity and mortality are urgently needed.