Surgical hypophysectomy was carried out for therapeutic purposes on 14 patients with advanced diabetic retinopathy. Eight of the 14 patients showed objective improvement for periods lasting from 2 1/2 to more than 6 years. Improvement consisted of maintenance or improvement in visual acuity and regression of neovascularization as evidenced by microaneurysms and macroaneurysms, new blood vessels, and hemorrhages diminishing or disappearing. More advanced changes in the retina and vitreous such as fibrosis, gliosis, and retinal separation remained static or progressed. The mechanism by which hypophysectomy induces improvement in diabetic vascular disease is unknown, but may be related to the amelioration of the metabolic defect as evidenced by the reduced requirement for insulin after surgery. Hypophysectomy should be considered in those patients whose diabetic retinopathy is progressive and threatens blindness. transfrontal craniotomy.12Trimethaphan (Arfonad) camphorsulfonate-induced hypotension was not employed in diabetic patients except for the first patient operated on. Insulin was omitted on the morning of surgery in the adult-type patient. In the juvenile-type diabetic patient, about one third the customary insulin dosage was given on the morning of surgery. In the first few postoperative days, regular insulin was administered at intervals as required. Insulin requirement in the immediate postoperative period was always considerably less