A retrospective study was made of 56 patients with squamous cell lung cancer, who were inoperable or unresectable and had completed a course of radiotherapy at Jichi Medical School Hospital from August, 1973 to December, 1986. All cases had a performance status score of 80-100 (Karnofsky), no evidence of a distant metastases and tumors that had received a minimum total dose of 50 Gy. The patients were treated with one of three therapy regimens: split course (SC, 32 Patients), conventional fractionation (CF, 13), or multiple daily fractionation (MDF, 11). The over-all median survival time was 13.0 months, and the 2 and 5-year survival rates were 29.2% and 14.7%, respectively. The patients treated with the split course had the lowest survival rate in comparison with the other two groups. Comparison of the patients with the continuous course (CF + MDF) were significantly higher (P less than 0.025) than that of the split course. Patients with MDF had better local control. Age, tumor stage, and the size of the booster field were found to be factors which influenced the survival rate with a fair statistical significance. The survival rate increased with an increase in age, a decrease in the tumor stage, and in the size of the booster field. These findings have important implications for the design of future clinical trials for patients with squamous cell lung cancer.