Two cases of bilateral renal cell carcinoma are reported. The first case is of a 54-year-old male who visited our hospital on March 7, 1984 complaining of colicky pain in his left flank. Intravenous urography showed a large mass in the upper pole of the left kidney causing deformity and dislocation of the upper calyces. There were no remarkable findings in the right kidney. Abdominal CT-scan and arteriography revealed a round and hypervascular tumor with soft tissue mass density in the upper pole of both kidneys. Nephrectomy of the left and segmental resection of the upper pole of the right kidney were performed on April 11, 1984. The second case is a 47-year-old male who visited our hospital complaining of total gross hematuria. Intravenous urography showed a large soft tissue mass at the lower pole of the left kidney. Abdominal CT-scan revealed a large tumor mass associated with central necrosis in the left kidney and also a small tumor lesion at the center of the contralateral kidney. Bilateral nephrectomy was performed on December 19, 1984, and the patient was referred to hemodialysis treatment. The cut section of the nephrectomized right kidney specimen revealed multiple minor accessory tumors. Both patients have been doing well without any evidence of recurrence or metastasis.