Renal cell carcinoma is diagnosed frequently when it already has metastasized. The use of immunotherapy has provided a new source of drugs to be used in the therapy of renal cell carcinoma. Interferons were the first biologics to be evaluated demonstrating a response rate of 10-30 percent. The second cytokine to be actively developed was interleukin-2, a T-cell growth factor which demonstrated activity in patients with renal cell carcinoma of 20-30 percent alone or in combination with LAK cells and other cytokines (such as interferons and tumor necrosis factor). Biologic response modifiers such as interferons and interleukins alone and in combination with other drugs have opened a new era in the therapy of renal cell carcinoma. Future development of other cytokines may pave the way for higher response rates with durable duration for this disease.