From June 1986 to February 1989, 103 patients with advanced non-small cell lung cancer, with no previous chemotherapy, were randomized to receive either a combination of cisplatin and vinblastine (group A) or the same combination with the addition of mitomycin (group B). In group A, 15/48 evaluable patients had objective responses, as did 8/45 in group B. The median survivals were 35 and 32 weeks, respectively. The median survival of patients with response or stable disease was 43 weeks. Response and survival did not differ significantly between treatment groups. The addition of mitomycin to the two-drug combination showed no major therapeutic benefit, while bone marrow toxicity was increased. Three patients in group B died of sepsis. Among the different patient characteristics, disease stage, performance status and response had influence on survival.