Patients with metastatic renal cell carcinoma have a very poor prognosis with a five-year survival rate of &lt;5%. Recently, biological therapies (e.g., interferons, interleukins, monoclonal antibodies) have demonstrated moderate anti-tumor activity in this disease. In some studies, over 30% of patients treated with alpha-interferons have exhibited a major response. Interferon treatment is associated with moderate toxicity, however, at present it is impossible to predict which subset of patients will benefit from interferon therapy. Monoclonal antibodies, while of limited therapeutic benefit, have been useful in diagnostic studies. Some of these antibodies identify as assortment of glycoproteins of varying molecular weights expressed on the cell surface of renal cancers.