Fifty-nine fresh osteochondral allografts were consecutively transplanted into the knees of fifty-eight patients. The preoperative diagnoses were chondromalacia or degenerative arthritis of the patella, osteochondritis dissecans, a traumatic defect or osteonecrosis of the femoral condyle, a painful healed depressed fracture or traumatic defect of the tibial plateau, and unicompartmental traumatic arthritis of the knee. All of the patients had disabling pain after the failure of previous attempts to correct the problem surgically. Thirty-nine patients (forty knees) were available for follow-up at two to ten years after the allograft was transplanted. Nine transplants (22.5 per cent) failed and thirty-one (77.5 per cent) were successful. The result was rated excellent after thirteen of the successful transplants, good after fourteen, and fair after four. Transplantation of a fresh osteochondral allograft proved to be a satisfactory intermediate procedure for the treatment of the disabling conditions, except unicompartmental traumatic arthritis, in the young patients in this series. For the patients who had unicompartmental traumatic arthritis, the rate of success was only 30 per cent.