Fifty patients with metastatic renal cell carcinoma were treated with recombinant interleukin-2 alone or in combination with the antitumor drug vinblastine or lymphokine-activated killer cells. Of 34 evaluable patients treated with intravenous bolus interleukin-2, 1 (3%) had a partial response. Vinblastine increased myelotoxicity but did not enhance response to interleukin-2 in 15 of these patients. Two partial responses were observed among 15 patients treated with lymphokine-activated killer cells in addition to interleukin-2. In 1 patient biopsy documented complete resolution of hepatic metastases lasting for 1 year was observed. All responders had undergone previous nephrectomy and none had multiple sites of metastatic disease. Toxicity was significant and caused termination of therapy in 40% of the patients. Biological therapy using interleukin-2 can result in prolonged responses in renal cell cancer but future trials should be directed at lessening toxicity.