During the recent 3 years since April 1985 percutaneous fine needle aspiration biopsy(Fn-AB) of 174 chest lesions was performed with Westcott needle (soltted 20G or 22G thin wall needle) in the department of diagnostic radiology of Hanyang University. There were 149 lung lesions(105 malignant tumors 34 benign lesions) and 25 mediastinal lesions. Positive diagn-osis in malignant lung lesions was established in 105 cases (100%) by FNAB, Among them 98 cases (93%) were diagnosed by cytlolgic examination and 94 cases (90%) were diagnosed by histologic examination. Specific diagnoses for benign lung lesions were made in 22 cases (65%) and for mediastinal lesions in 13 cases (52%) The histlolgic specimens obtained from FNAB can make further confirmation of the result of cytology and improvement of diagnostic accuracy. 19 patients developed pneumothorax and 5 of them required treatment,.Minimal hemoptysis was found in 7 patients. FNAB of the chest lesions is prefered diagnostic method because of its safety simplicity and accuracy