From March 1986 to June 1990, the percutaneous Fine Needle Aspiration Biopsy[FNAB] of 102 thoracic lesions were performed with Westcott needle [slotted 20G or 22G thin needle], for the purpose of identifying and diagnosing thoracic lesions. There were 94 lung lesions [67 malignant tumors, 27 benign lesions] and 8 mediastinal and chest wall lesions. The results of FNAB were compared with sputum cytology and bronchoscopic examinations. The sputum cytologic examinations were performed in 54 cases of malignant lung tumor and the malignant cell was found at the 18 cases [33%]. We bronchoscopic examinations were performed in 24 cases and the malignant cell was found at the 12 cases [55%]. The positive diagnostic rate of malignancy was 100% by FNAB. Among them, 55 cases [82%] were diagnosed by cytologic examinations and 43 cases[64%] by both. The specific diagnoses for benign lung lesions in 15 cases[55%] and for mediastinal and chest well lesions in 5 cases[62%]. The 7 patients[6.9%] developed the pneumothorax and 5 of them required the treatment. Therefore, the FNAB of thoracic lesions may be a preferred diagnostic method because of its safety, simplicity and accuracy.