The approach to the treatment of patients with metastatic renal cell carcinoma has changed dramatically during the past 5 years. In the past, efforts to treat metastatic renal cell carcinoma were directed at palliation using chemotherapy, hormonal agents, or radiation therapy to control symptoms. Metastatic renal cell cancer was often resistant to these agents. With the advent of biological response modifiers, an entirely different approach is now available. Both recombinant human interferon-alpha (IFA-alpha) and interleukin-2 (IL-2) have significant activity in advanced renal cell carcinoma. Treatment with IFN-alpha can be given as outpatient therapy and provides effective disease control in a substantial minority of cases. Treatment with IL-2-based therapy, although associated with significant acute toxicity, is capable of inducing durable remissions from this otherwise lethal disease.