BACKGROUND Renal cell carcinoma (RCC) is relatively resistant to both chemotherapy and radiotherapy. Response and survival of treatment with Interferon-alpha (IFN-alpha) and Interferon-gamma (IFN-gamma) were evaluated in patients with metastatic RCC. METHODS Thirty-one patients with confirmed RCC were included in this study. Fifteen of 31 patients received injection of IFN-alpha and IFN-gamma three times a week. IFN-gamma was infused subcutaneously by microinfusion pump. Sixteen received IFN-alpha alone more than three times a week. RESULTS The overall response rate was 20.0% in the IFN-alpha and IFN-gamma group, and 12.5% in the IFN-alpha alone group. Long lasting stabilization of the disease (more than; 12 months) was seen in 92.3% of CR, PR or SD in the IFN-alpha and IFN-gamma group, as compared with 71.4% in the IFN-alpha alone group. Both groups differed significantly in survival rate from the first treatment with IFN (p < 0.05). CONCLUSIONS A long lasting stabilization of the disease can be expected in patients who were treated with our regimen of IFN-alpha and IFN-gamma.