From January, 1963, to January, 1977, 4 cases of acute allograft rupture occurred in 474 renal transplants performed at the Cleveland Clinic, an incidence of 0.8 per cent. Rupture developed between the fifth and sixteenth day after transplantation during a period when the patients required dialysis because of poor allograft function. All patients had surgical exploration and successful repair of the laceration. Biopsies in each case at the site of laceration revealed findings consistent with acute allograft rejection. The rejections were mild in 2 cases, moderate in one, and severe in another. Two kidneys failed to sustain function, and the patients were returned to chronic hemodialysis two to five months later. None required a nephrectomy. The other two kidneys are functioning well, with serum creatinine values of 1.3 and 1.5 mg./100 ml. one year after allograft rupture. Since rupture of a renal allograft does not appear to increase the intensity of rejection nor does it represent a severe type of rejection, transplant nephrectomy can be avoided unless hemorrhage is uncontrollable from the site of laceration.