This paper reports two cases of acquired renal cysts and multiple renal cell tumors in end-stage kidneys with a discussion of the pathogenesis of these lesions. The first patient had been on maintenance dialysis for approximately three years when he was found to have multiple renal cysts and renal cell tumors. He subsequently developed multifocal urothelial carcinomas of the lower urinary tract. The second patient had progressive renal failure due to hypertensive vascular disease when he underwent left nephrectomy because of multiple renal cysts and renal cell carcinoma. He later developed terminal renal failure and was maintained on chronic dialysis. He expired three years later. At autopsy, the right kidney also demonstrated multiple cysts and renal cell tumors.