A case of renal cell carcinoma effectively treated by interferon-alpha and the embolization of the left renal artery is reported. A 69-year-old man was referred to us because of a left renal mass. We made a diagnosis of a left renal tumor with tumor thrombus in the renal vein and inferior vena cava, and multiple lung metastases by imaging examinations. At first the embolization of the left renal artery was selected and interferon-alpha treatment was performed for 3 months. At 3 months after the embolization, the metastatic lung tumors had completely disappeared and the left renal tumor and the tumor thrombus were reduced in size, so that left radical nephrectomy was performed. Pathological examination revealed that a small part of the tumor was viable renal cell carcinoma. After the operation, interferon-alpha treatment has been continued for 15 months and recurrence and metastasis have not been detected.