We have studied 93 lung cancer patients, who were treated in this hospital for the past eleven years, with regard to the factors which influence the prognosis, by figuring out the survival curve, and obtained the following results. 1) Of various treatments, operation is the most favourable for the median survival and combination-therapy of irradiation and chemotherapy is the second, and chemotherapy only is the least favourable. In chemotherapy cases, the median survival shows little difference between different drugs used. 2) Of each clinical stage, Stage Ⅰ is the most favourable, Stage Ⅱ is the second, and Stage Ⅲ and Stage Ⅳ is not favourable for the median survival. In chemotherapy cases, patients with Stage Ⅰ+Stage Ⅱ are the longest in the median survival, but their survival is shorter comparing with the total cases of Stage Ⅰ+Stage Ⅱ. 3) In 58 cases, whose cell types were defined, the median survival of adenocarcinoma cases is the longest, and that of undifferentiated carcinoma cases the second and that of epidermoid carcinoma cases the shortest. 4) In two groups of patients which are divided before and after 1968, the median survival of latter groups is apparently long, but in the cases treated with chemotherapy, the median survival of the two groups show little difference, although the latter group contains many effective cases. 5) In three groups according to the therapeutical effects ('improvement', 'no change', 'aggravation'), the median survival of the group of 'improvement is the longest, but the group of 'no change' shows almost the same survival, indicating there is no strict correlation between the prolongation of life and effect of chemotherapy. The results stated above lead to the following conclusions. Ⅰ) For the improvement of the prognosis of lung cancer, early detection and operation should be done. Ⅱ) The advanced cases had better be treated with the combination therapy of radiation and chemotherapy. Ⅲ) At present, the effect of chemotherapy is not as great as it should be, but could be improved by minimizing its side effects.