The use of antihypertensive drug treatment has altered the natural history of hypertension. Whereas congestive heart failure, cerebral hemorrhage, and renal failure were the major complications of untreated severe hypertension, myocardial infarction and thrombotic stroke have emerged as major problems in treated hypertensive patients. None of the major therapeutic trials in hypertension have provided evidence that reducing blood pressure reduces the risk of atherosclerotic complications of hypertension. Hypertension certainly aggravates the severity of atheromatous lesions in experimental animals, and may do so in humans. However, atherosclerosis is more closely related to disturbances in lipoprotein metabolism than to other factors. The common finding that serum cholesterol is raised in hypertensive patients may be due to atherosclerosis being the primary lesion, and hypertension a secondary complication rather than hypertension being the primary lesion.