Terminal chronic renal failure was discovered in a patient who had received CCNU 1 940 mg/m2 during the previous two years. The renal function was normal before treatment, and there was no evidence of other causes of renal failure. The clinical picture was identical with that observed in patients receiving such treatment and recently published. This case emphasizes the need for limiting the dose of nitrosyl-urea compounds to 1 200 mg/m2 and for monitoring the renal function very closely during and towards the end of the treatment.