The split-course concurrent thoracic radiation therapy (TRT) and full-dose chemotherapy for unresectable stage III non-small cell lung cancer (NSCLC) has produced promising results by comparison with the sequential approach. Instead of split-course radiation, we conducted a phase II study to investigate the feasibility of continuous concurrent TRT and chemotherapy. Twenty-two patients with unresectable NSCLC were enrolled onto a phase II study of continuous concurrent radiotherapy and chemotherapy. Treatment consisted of two courses of cisplatin (80 mg/m(2) on days 1 and 29), vindesine (3 mg/m(2) on days 1, 8, 29 and 36), and mitomycin (8 mg/m(2) on days 1 and 29). TRT began on day 2 at a dose of 60 Gy (2 Gy per fraction and 5 fractions per week for a total of 30 fractions). Of 22 patients assessable for response, none achieved a CR and 17 (77.3%) achieved a PR with an overall response rate of 77.3% (95% confidence interval, 54.6-92.2%). Grade 3 or 4 leukopenia was observed in 5/13 (81.8%) patients. Six patients (27.3%) experienced > or = grade 3 thrombocytopenia. Non-hematological toxicity was relatively mild. The overall median survival time was 19.0 months and the 1- and 2-year survival rates were 84.8 and 34.5%, respectively. It was possible to administer two courses of chemotherapy in 18 patients (81.8%) as planned. Nineteen (86.4%) of the 22 patients received the planned 60 Gy radiation. It seems to be difficult to administer the planned treatment without any interruption for the majority of patients. However, in the selected patients who completed the 60 Gy TRT, nearly half of the patients completed TRT without interruption. This combination regimen is considered to be feasible on condition that the stopping rule of the treatment is followed. We recommend administering radiotherapy continuously as far as possible.