Combined treatment of UFT with cisplatin (CDDP) achieved remarkable elongation of survival time of BDF1 mice, which were intravenously transplanted with Lewis lung carcinoma (LLC). Three cycles of weekly iv administration of CDDP and vindesine (VDS), and daily oral administration of UFT were scheduled. Combination UFT (18 mg/kg/day) with CDDP (6.0 mg/kg/day) yielded tumor-free survivors in all of the treated animals with slight body weight loss. Its efficacy was superior to that of the combination of CDDP with VDS. Supra-additive cytotoxic activity against LLC cells was observed by Isobologram method on the schedule of the exposure to 5-fluorouracil preceding the exposure to CDDP. Additive effect was observed by the reversed schedule of the treatment. Using human non-small-cell lung cancer (NSCLC) cell lines which derived from histologically different type, additive or greater additive sensitivity to both of the sequential treatment schedules with 5-FU and CDDP was observed. These results suggest that the combination chemotherapy of UFT with CDDP for lung cancer may show high antitumor efficacy with low toxicity in a clinical setting.