Evidence is presented to indicate that in some types of hypertension, especially in early essential hypertension, the circulation is hyperdynamic. With progression of vascular disease and increased arterial pressure, the increased cardiac output becomes normal and ultimately, with cardiac involvement, subnormal. Beta-adrenergic blocking drugs have been used to normalize this hyperdynamic circulation and reduce arterial pressure. Whether or not this therapy given over a long period inhibits the pathogenetic presser mechanisms, thereby preventing development of severe hypertensive vascular disease, remains to be demonstrated.