A 39-year-old man with a 13-year history of hemodialysis was hospitalized with left back pain in May 1989. The plain radiograph showed a calcification in the left kidney. Ct scan demonstrated a round high density area. We could not exclude the possibility of malignancy, therefore, we performed left nephrectomy. Pathological examination revealed that a tumorous mass in the renal parenchyma and renal adenocarcinoma was confined to the mass intermingled with the deposition of the oxalate crystals. It was difficult to diagnose. Therefore we recommend nephrectomy when the diagnosis is uncertain.