Two hundred and seventeen patients underwent diagnostic rigid bronchoscopy or bionchofiberscopy to evaluate the cytologic diagnosis in the lung cancer patient at the department of chest surgery of Yon-Sei university, college of the medicine from 1971 to 1977 year. One hundred and twenty cases of these patients were taken rigid bronchoscopy and ninety four cases of these patient were taken bronchofiberscopy. Cytologic examination of the sputum was done in 214 cases and sputum cytology was positive in 50 cases [23.4%]. Rigid bronchoscopy was made in 120 cases and this bronchoscopic cytology including bronchial washing and bronchial biopsy was positive in 34 cases [28.5%]. Bronchofiberscopy was performed in 94 cases and was positive in 45 cases [47.5%]. Histopathologically, 41 cases [43.6%] were epidermoid cell carcinoma, 8 cases [8.5%]of undifferentiated cell type, 12 cases [12.8%]of adenocarcinoma, 8 cases [8.5%]of alveolar cell type, and the 25 cases were undetermined. Cytologic examination of the sputum lacks the accuracy of the bronchoscopies in terms of both localization and accurate histologic indentification of the type of neoplasm. Rigid bronchoscope has the advantage of permitting identification of a tumor in a central location and of providing a sufficient amount of biopsy material for accurate diagnosis of carcinoma. However, it has the disadvantage of limiting examination to the larger, more central portions of the tracheobronchial tree. Bronchofiberscope had the advantage of examine upper lobe as well as other portions of the tracheobronchial tree which could not be visualized with the rigid bronchoscopy. A positive diagnosis in bronchofiberscopy was obtained in the highest rate, 47. 8% [45 cases]. A1 last, if a bronchogenic carcinoma is suspected on the basis of either symptoms of an abnormality on the chest film the diagnostic work-up-sputum cytology, bronchial washing, bronchoscopic biopsy, scalene node biopsy, thoracentesis and mediastinoscopy explothoracotomy etc-should precede in an attempt not only to obtain the higher positive diagnosis but also to obtain a tissue diagnosis and to evaluate the stage of the disease and to ascertain the appropriate mode of therapy.[KTCS 1978;2:129-146]