Operation is contraindicated in acute cerebral insults and neurological lesions which are already irreversible. A complete obstruction in the region where the great vessels branch off from the aorta are always surgically treated if the vessels distal to the lesion are still patent. Aneurysms in the aortoiliac region require resection and reconstruction of the vessels, stenoses and obliterating changes need reconstructive interventions. Angina mesenterica must be surgically treated if at least two intestinal arteries are damaged. Operative intervention in renal arteriosclerosis is only justified if hypertension is also present. Conservative therapy consists of prophylaxis or elimination of the risk factors, of the medical treatment of hyperlipemia and of inhibition of thrombocyte function.