The authors report series of 360 cases of transthoracic fine-needle aspiration cytology(TFNA) from Oct, 1982, through Aug. 1986 at the Seoul National University Hospital. A diagnosis of neoplastic lesion was established in 50.3% of the cases. A non-neoplastic diagnosis was made in 38.5%, nondiagnostic one in 6.5% and inadequate one in 4.7% of the total. Statistical findings on cytological diagnoses were as follows. Specificity was 100% ; sensitivity, 92%; predictive value for positive, 1.0 ; predicitive value for negative, 0.9 : concordance rate, 84.2% ; diagnostic accuracy in non-neoplastic lesion, 65.4%, and typing accuracy in malignant tumor, 0.77.