During recent years there has been increasing interest in the blood lipids in patients with diabetes mellitus, chiefly because of the uncertain relationship between dietary fat, hypercholesteremia and the frequent development of atherosclerosis in diabetic subjects. It has been repeatedly demonstrated that atherosclerosis can be produced in rabbits by feeding large amounts of cholesterol. It is also well known that many diabetic patients have hypercholesteremia, that arteriosclerosis develops at a relatively early age in many diabetic patients and that this complication accounts for most of the incapacitation and fatality from this disease. The cause of a high cholesterol content of the blood and of vascular disease in diabetic patients has naturally been the subject of much investigation. Before the advent of insulin it was necessary for all patients with diabetes except those with mild involvement to live on a high fat-low carbohydrate diet. Since 1922, with the use of insulin,