Lung cancer has become one of the most common cancers in Korea. Once signs, symptoms, or screening studies suggest this disease, it is of paramount importance to establish a tissue diagnosis of malignancy and determine the histologic cell type because of different treatment modality in small cell bronchogenic carcinoma. Currently, cytologic examinations including sputum, bronchial washing and brushing are widely used to diagnose and determine cell type in lung cancers. To evaluate the diagnostic yield and its accuracy of each diagnostic method in lung cancer, we have studied with 281 cases of histologically-proven lung cancer patients. The results are summarized as follows; 1) The diagnostic yields of bronchoscopic biopsy, bronchial washing, bronchial brushing, sputum cytology and PCNA (percutaneous needle aspiration) were 74,8% (86,4% with visible bronchoscopic lesion), 48.4%, 66,7%, 58.8% and 90.7%, respectively. 2) The diagnostic accuracy of each diagnostic method in the order named, was 96,8%, 93.4%, 87.3%, 86.9% and 86,8%. In consideration of mixed forms, this value was 98.1%, 93.4lo 89.2%, 89.7%, and 92.6%, respectively. 3) The cytologic examination of percutaneous needle aspriate of lung was the most useful, single test among the cytologic examinations. 4) It is appropriate in lung cancer to repeat the cytologic studies of sputum up to 5 times.