Eleven selected patients with a history of cancer have received renal transplants. In three patients the malignancies were diagnosed and treated before renal failure developed, two patients underwent bilateral nephrectomies for the treatment of bilateral renal malignancy. In six patients the malignancy developed while they were uremic, and they received transplants after treatment of the tumor. Recurrent tumor developed in only One of the 11 (9 per cent) patients after receiving the transplant. Thus, patients with a history of malignancy can receive a transplant without accelerating growth of the tumor. We recommend a minimum period of one year between tumor treatment and transplantation to observe for tumor recurrences or metastases. A longer period of observation may be necessary in patients who have tumors with a poorer prognosis.