A total of 61 evaluable patients with advanced renal cell carcinoma have been treated with 3 x 10(6) IU per square meter of body surface with recombinant alpha 2b interferon three times a week within a Cooperative Phase II Study. Toxic death for terminal renal failure occurred in 1 patient (1.63%), and toxicities greater than WHO grade 2 were present in 10 cases (16%). The overall response rate after six months of treatment was 13.1% (partial response 4, minor response 4). Two complete responses were obtained at nine and fifteen months (3.3%). Long-lasting stabilization of disease was 13.1 percent.