From August, 1979 to June, 1990, 226 cases of primary lung cancer were treated surgically at our Department. Of these, 176 cases, excluding hospital deaths from lung cancer and other diseases, were analyzed according to prognosis. The 5-year survival rate of the 176 cases was 40.2% and the 5-year survival rates according to sex were, male, 36.1%; female, 53.2%. The 5-year survival rates according to postoperative stage were, stage I, 64.1%; stage II, 44.1%; stage III A, 22.1%; stage III B & IV, 0% and the 5-year survival rates according to histologic type were, adenocarcinoma, 40.5%; squamous cell carcinoma, 49.7%; large cell carcinoma, 18.9%; small cell carcinoma, 0%. The 5-year survival rates according to primary site were, right side, 43.8%; left side, 34.6%; right upper lobe, 39.7%; right middle lobe, 60.0%; right lower lobe, 44.4%; left upper lobe, 41.7%; left lower lobe, 18.1%. The prognosis of squamous cell carcinoma, and the early stage, female group, right side group, right middle & lower lobe group, were all fairly good.