The clinical observations on the bronchogenic cancer of one hundred sixty cases treated in the Department of Thoracic Surgery, Seoul National University Hospital are as follows: 1] Most of them,. 90 percent of the cases were over 40 years of age and male was predominated over female with sex ratio of 6 to 1. 2] The average duration of symptoms before the first examination was about 5 months arid the most common complaints were cough, chest pain, breathing difficulty and blood-tinged sputum. 3] In ninety-four cases[59%] thoracotomy was undertaken with resection of the lesion in 52 cases[33% ]. 4] Histopathological diagnoses made in 141 cases were squamous cell carcinoma in 47.5%, undifferentiated cell carcinoma in 33.3%, adenocarcinoma in 9.2,% and alveolar cell carcinoma in a single case.[KTCS 1974;1:31-36]