Renal cell carcinoma (RCC) represents an unusual solid tumor for which no treatment other than surgical therapy has been effective. The remarkable heterogenous behavior of this tumor and the documented rare spontaneous regressions suggest an unusual sensitivity to host immunologic control. In recent years, exciting developments in molecular genetics, growth factors, modulators of invasion of metastases, and cytokine-lymphocyte interactions have produced new hypotheses and a wealth of information regarding the origin, behavior, and control of RCC. Interest in the immunotherapy of metastatic RCC has recently increased with the demonstrated reproducible tumor responses obtained with recombinant human interferon-alpha or interleukin-2. Durable clinical remissions in some patients with advanced RCC can now be achieved by using cytokine therapy alone or in combination with activated killer cells. This article reviews the current understanding of the basic biology of RCC, surgical approaches to localized RCC, and biologic therapy for advanced disease.