Eighteen patients with advanced renal cell carcinoma were treated with human lymphoblastoid interferon (Wellferon) and continuous fusion vinblastine. All patients received vinblastine as a continuous infusion at a dose of 1.5 mg/m2/day on days 1 to 5. The interferon was given by daily intramuscular injections on days 1 to 10. Three patients were treated with a dose escalation scheme that reached a maximum daily dose by day 3 of 5 X 10(6) units/m2/day and that was then continued until day 10. Fifteen patients received 3 X 10(6) units/m2/day on day, 1, and 5 X 10(6) units/m2/day on days 3 to 10. Treatments were repeated every 28 days. Neutropenia (less than 1,500/mm3) occurred in 14 of 18 patients. Transient increases in serum glutamic-oxaloacetic transaminase levels to greater than four times baseline were noted in nine patients. Thrombocytopenia (less than 100,000 platelets/mm3) occurred in one patient. Fatigue, lethargy, and decline in performance status were marked in four of the patients. None of the patients in the low-dose interferon group and only 1 of the 15 patients in the high-dose interferon group had an objective response (7%, with a 95% confidence interval of 0 to 31%). Of the 12 patients completing at least two courses of therapy, 10 were in the high-dose group, which included the 1 objective (partial) response. This response noted at the start of the fourth course. Ten others developed progressive disease and one stopped treatment because of neurologic toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)