PURPOSE: To evaluate the survival and prognostic factors in patients with stage III non-small cell lung cancer treated with curative radiotherapy alone or combined with chemotherapy. MATERIALS AND METHODS: A retrospective analysis was undertaken of 35 patients who had locally advanced non-small-cell lung cancer and t treated with curative radiotherapy in Department of Therapeutic Radiology, Kangdong Sacred Heart Hospital, from January 1991 through December 1993. According to AJCC staging, 15 patients were stage IIIA, and 20 were stage IIIB. Radotherapy was delivered with 1.8-2 Gy per fraction/day, 5 days per week using 6 MV X-ray, to a total dose ranging from 48.8 Gy to 66.6 Gy(median, 61.2 Gy) in 4 to 9 weeks. Ten patients received neoadjuvant or concurrent chemotherapy with FIP (5-FU, ifosfamide, and cisplatin) or FP(5-FU and cisplatin). RESULTS: For all patients, median survival was 6 months, 1-year and 2-year survival rates were 23.3% and 6.7%, respectively. The median survival was 8 months in stage IIIA and 5.5 months in stage IIIB. In patients treated with radiation therapy alone, median survival was 5 months and 1-year survival rate was 9%. In patients who received chemotherapy, median survival was 11 months and 1-year survival rate was 60%. The difference of survival between these two groups was statistically significant (p=0.03). Total radiation dose, degree of response, and post-treatment ECOG score were also significantly associated with survival. But it was not affected by age, sex, pretreatment ECOG score, presence or absence of weight loss, tumor location, pathologic type, N stage, and degree of response to treatment. CONCLUSION: Conventional radiotherapy alone is unlikely to achieve long term survival in patients with stage III NSCLC. Radiotherapy with altered fractionation schedule or multimodality treatment combined with surgery and/or chemotherapy should be considered if feasible.