Renal cell carcinoma (RCC) evokes an immune response, which has occasionally resulted in spontaneous and dramatic remissions [1-3]. In an attempt to reproduce or accentuate this response, various immunotherapeutic strategies have been studied. The most consistent anti-tumor activity has been reported with interferon alfa (IFN-alpha) and interleukin 2 (IL-2). In recent years, randomized trials have suggested that high-dose intravenous bolus IL-2 is superior in terms of response rate and possibly response quality to regimens that involve either low-dose IL-2 and IFN-alpha, intermediate- or low-dose IL-2 alone, or low-dose IFN-alpha alone. As this list of effective therapies for RCC grows, improvements in patient selection will be necessary to ensure that the only therapy capable of producing durable remissions will remain available to the patients who should receive it [4-7].