PURPOSE: We evaluated retrospectively the outcomes of inoperable squamous cell lung cancer patients treated with radiotherapy to find out prognostic factors affecting survival. MATERIALS AND METHODS: Four hundred and eleven patients diagnosed as squamous cell lung cancer between November 1988 and December 1997 were the basis of this analyses. The planned dose to the gross tumor volume was ranged from 30 to 70.2 Gy. Chemotherapy was combined in 72 patients (17.5%) with the variable schedule and drug combination regimens. Follow-up period ranged from 1 to 113 months with the median of 8 months and survival status was identified in 381 patients (92.7%). Overall survival rate was calculated using the Kaplan-Meier method. RESULTS: Age ranged from 23 years to 83 years with the median 63 years. The male to female ratio was about 16:1. For all 411 patients, the median overall survival was 8 months and the 1-year survival rate (YSR), 2-YSR, and 5-YSR were 35.6%, 12.6%, and 3.7%, respectively. The median and 5-YSR were 29 months and 33.3% for Stage IA, 13 months and 6.3% for Stage IIIA, and 9 months and 3.4% for Stage IIIB, respectively( p=0.00). The median survival by treatment aim was 11 months in radical intent group and 5 months in palliative, respectively ( p=0.00). Of 344 patients treated with radical intent, median survival of patients (N=247) who received planned radiotherapy completely was 12 months while that of patients (N=97) who did not was 5 months ( p=0.0006). In the analyses of the various prognostic factors affecting to the survival outcomes in 247 patients who completed the planned radiotherapy, tumor location, supraclavicular LAP, SVC syndrome, pleural effusion, total lung atelectasis and hoarseness were statistically significant prognostic factors both in the univariate and multivariate analyses while the addition of chemotherapy was statistically significant only in multivariate analyses. The acute radiation esophagitis requiring analgesics was appeared in 49 patients (11.9%) and severe radiation esophagitis requiring hospitalization was shown in 2 patients (0.5%). The radiation pneumonitis requiring steroid medication was shown in 62 patients (15.1%) and severe pneumonitis requiring hospitalization was occurred in 2 patients (0.5%). During follow-up, 114 patients (27.7%) had progression of local disease with 10 months of median time to recur (range : 1~87 months) and 49 patients (11.9%) had distant failure with 7 months of median value (range : 1~52 months). Second malignancy before or after the diagnosis of lung cancer was appeared in 11 patients. CONCLUSION: The conventional radiotherapy in the patients with locally advanced squamous cell lung cancer has given small survival advantage over supportive care and it is very important to select the patient group who can obtain the maximal benefit and to select the radiotherapy technique that would not compromise the life quality in these patients.