A pilot study of a combination therapy comprising of consecutive oral administration of UFT, and two-part divided administration of CDDP was undertaken in patients with inoperative non-small cell lung cancer, based on the synergistic effects of CDDP and 5FU. UFT was administered orally at a dosage of 400 mg/m2 for two consecutive weeks (Day 1-Day 14) and CDDP was administered twice by intravenous infusion, once on Day 4 and again on Day 8. The unit dose of CDDP was increased sequentially, from 40 mg/m2 in step 1, to 50 mg/m2 in step 2, and then to 60 mg/m2 in step 3, with safety being confirmed during the process. The numbers of patients registered for each dose level were 3, 3, and 20, respectively. Evaluation of toxicities could be conducted for all the patients except one. No toxicities of grade 3 or higher were observed in step 1 or 2. There was no problem with continuous administration of UFT. The following toxicities of grade 3 or higher were observed in step 3: leukocytopenia in 2 patients; reduction of the hemoglobin count in 1; decrease in creatinine clearance in 2; anorexia in 3; and nausea and vomiting in 3. Bone marrow suppression was mild and transient. Renal failure and digestive symptoms, which were proved to be transient and treatable by symptomatic treatment, were also observed. The step 3 administration was effective in 8 (47.1%) of the 17 patients with measurable lesions (95% CI: 23-71%). In conclusion, since it was determined that the dose employed in step 3 should be recommended and that it could be expected to exhibit antitumour effects with mild bone-marrow suppression, a large scale phase II study should be conducted in no prior treatment non-small cell lung cancer.