Perhaps no other variation in the physiologic functions of the body has been subjected to as much investigation as has the blood pressure. The search for the cause of hypertension continues while newly discovered methods of therapy in hypertensive disease are being made available to those having this condition. Master et al.1 defined hypertension, concluding that prior to 1952 the concepts were incorrect or misleading in that the critical levels established to divide normal from abnormal blood pressure were too low. The wide variations in blood pressure levels in a selected group of 1,522 patients with essential hypertension were observed over a long period by Hines.2,3 Clinical hypertensive disease frequently developed among his subjects if the diastolic pressure was greater than 85 mm. Hg. Among the first observers to report on variable blood pressure and its apparently adverse effect on morbidity and mortality were Levy et al.,4,5