We examined renal-transplant tissue from 12 diabetic and 28 nondiabetic patients who had had a renal graft for at least two years. In 10 diabetic patients arteriolar hyalinosis lesions developed in the graft. In six these lesions involved both afferent and efferent limbs of glomerular arterioles — a pathological finding virtually diagnostic of diabetes mellitus. In all cases these lesions were present within five years of transplantation. Only three of the 28 nondiabetic patients had hyaline vascular changes (P<0.001), which occurred only in rare vessels, did not appear within the first five years after transplantation and did not involve both afferent and efferent arterioles. One diabetic patient had nodular glomerulosclerosis. Thus, the first clearly distinguishable lesion of diabetes to occur with frequency in normal kidneys transplanted into diabetic patients is arteriolar hyalinosis. (N Engl J Med 295:916–920, 1976) Renal transplantation is an effective means of treatment for end-stage renal disease due to a variety of pathologic processes, including diabetic nephropathy.1 Renal transplantation in patients with advanced diabetic nephropathy also provides a unique opportunity to answer fundamental pathogenetic questions regarding the secondary complications of diabetes mellitus in man. Controversy still rages over whether these complications are secondary to carbohydrate intolerance or whether the microangiopathy of diabetes is determined by a separate genetic disorder.2 3 4 5 It is known that in kidneys of rats with long standing chemically induced diabetes glomerular lesions develop that are reversible upon transplantation of these organs into.