We report a case of renal cell carcinoma in a 76-year-old man with pulmonary metastasis and tumor thrombus in inferior vena cava. The patient responded to the combination therapy with a small amount of HLBI (human lymphoblastoid interferon-alpha) and UFT (1:4 mixture of tegafur and uracil). HLBI was administered intramuscularly at a dose of 3 x 10(6) IU two times a week. However, the administration of the same dose was discontinued, because of the severe side effects, such as depression, general fatigue, anorexia and high fever. Finally, the maximum dose was determined to be 2 x 10(6) IU/week. Nine weeks after the first treatment, UFT was simultaneously given orally at a dose of 100 mg/day for potentiating the antitumor effect. At 12 weeks, the patient registered complete response of pulmonary metastasis, and partial response (83% reduction) of renal tumor. About 60 x 10(6) IU HLBI was administered until the response was noted. After 34 weeks of administration of HLBI, nephrectomy was performed. Histological diagnosis was renal cell carcinoma of clear cell subtype, grade 2. Microscopically, many lymphocytes infiltrated into the cancer cells. This suggests the possibility of immunological response caused by HLBI.