Four renal homotransplants were carried out between cadaver donors and four recipients, all of whom were in terminal chronic renal failure. Immune suppression was attempted with azathioprine (Imuran), actinomycin C and prednisone; no radiation was used, nor were the recipient's kidneys, spleen or thymus removed. One patient died with disseminated histoplasmosis at two weeks; another with irreversible homograft rejection at 30 days; a third patient died of septicemia after 9(1/2) weeks with stable renal function. The fourth patient, whose transplant had been ischemic for 190 minutes and had not functioned for 2(1/2) weeks thereafter, eventually achieved good function which remained unchanged to 7(1/2) months. Changes in urinary enzyme excretion and in the I(131) renogram and meralluride scan were of value in assessing homograft rejection.