Out of 67 patients accepted for maintenance dialysis (56 for hemodialysis and 11 for peritoneal dialysis) 47 had not received any form of immunosuppression either in connection with renal transplantation or as part of the therapy for their intrinsic renal disease. Six out of the 47 patients (12.8%) were found to have malignancies which were not directly causing their renal failure. Two patients had carcinomas of the kidney, 2 patients had skin cancers, 1 patient had a carcinoma of the stomach and 1 patient had a carcinoid tumour of the small intestine. This raises the question whether prolongation of uremia by long term dialysis may contribute to the development of malignancy by increasing longevity in the chronically immunosuppressed uremic state.