Using a randomized prospective trial design, chemotherapy with 5-fluorouracil, vincristine, and mitomycin C (FOMi) was compared with cyclophosphamide, doxorubicin, and cisplatin (CAP) and with FOMi alternating with CAP (FOMi/CAP) in 452 eligible patients with metastatic large-cell undifferentiated and adenocarcinoma of the lung. Objective responses were obtained in 26%, 17%, and 22% of patients treated with FOMi, CAP, and FOMi/CAP, respectively. The median survival was similar for FOMi, CAP, and FOMi/CAP therapies (20, 24, and 23 weeks, respectively), but the overall survival (log rank test), 1-year survival, and remission duration were longer for FOMi/CAP-treated patients. Survival was significantly longer for fully ambulatory FOMi/CAP-treated patients compared with either FOMi (P = .01) or CAP (P = .04). Younger patients treated with full doses of therapy responded more often than older patients receiving reduced drug doses (26% and 11%, respectively; P = .003). A prognostic factor regression analysis of all eligible patients indicates that sex, performance status, stage, and treatment assigned were important independent variables determining survival (P less than .05). Toxicity was comparable in each treatment group.