As of today, the frequency of primary lung cancer is one of the improved problems in modern medicine and is increasing rapidly year by year. This study dealed with 138 cases of primary lung cancer proved by histopathologic examination in Thoracic & Card iovascular Surgery Dept. of N.M.C. from Sept. 1966 through June 1981. The majority of patients belong to 5th and 6th decade. Ratio between male and female was 3.7: 1. Initial symptoms were cough, blood tinged sputum, hemoptysis, chest pain, dyspnea and duration of symptoms before admission was within 6 months [60%] and 12 months [78%]. Histopathologically, 64 cases [61%] of them were the squamous cell carcinoma, 21 cases [15%] were the adenocarcinoma, 20 cases [14.8%] were the anaplastic carcinoma. Fifty-six cases were resectable: 43 cases were subjected to pneumonectomy and 13 cases were to lobectomy. The remaining 82 cases were nonresectable, but exploratory thoracotomy was performed in 22 cases of them. Among 56 resected cases, 33 cases were radically operated and 17 cases were subjected to palliative operation and 6 cases were subjected to extended operation. [Concomitant pericardium resection in 1 case and concomitant chest wall resection in 5 cases]. Surgical mortality was 10.7% and causes of death were aspiration of contralateral lung, respiratory insufficiency, postop. empyema with B.P.F, cardiogenic failure. This study analysed the cancer stage between preop clinical T.N.M. stage and postop. T.N.M. stage in 78 cases; resectable 56 cases and non-resectable 22 cases. [KTCS 1982;3:278-284]