Late complications generally related to immunosuppressive therapy may develop in patients whose renal homotransplants have survived six months. Therapy with azathioprine alone is well tolerated, but addition of corticosteroids increases the risk of lethal infection, fat embolism, aseptic bone necrosis, osteoporosis, diabetes, obesity, and bleeding duodenal ulcers. Mercaptopurine which can cause bone marrow depression is potentiated by allopurinol and perhaps phenylbutazone (Butazolidin). Late renal complications include progressive hypertension and chronic rejection with gradual loss in kidney function and increase in proteinuria. Autoimmune glomerulonephritis in patients with circulating antiglomerular basement membrane antbodies has been reported. Gastrointestinal complications include pancreatitis and malabsorption. Abnormalities in hepatic function may also occur and may be related to azathioprine toxicity. Transplant recipients have also manifested metastatic carcinoma which, in some patients has been immunologically rejected when immunosuppressive therapy was discontinued.