Metastatic renal cell carcinoma has a poor prognosis. The efficacy of immunotherapy with interferon alpha (IFN-alpha) or interleukin 2 (IL-2) or their combination has been investigated extensively. The best schedule and optimum dose and combination is not known. On the basis of three prognostic factors, viz. WHO performance score, time between initial diagnosis and treatment of metastases, and number of metastatic sites, patients can be divided in prognostic groups. Patients classified in the favourable or intermediate prognostic group may survive longer after immunotherapy and therefore are candidates for such therapy. Patients who are classified in the poor prognostic group will not profit from any known systemic therapy.