OBJECTIVE CT-guided percutaneous transthoracic fine needle aspiration biopsy (PTFNAB) was performed in small peripheral pulmonary lesions, which are not easily diagnosed or accessible to fibrobronchoscopes. METHODS Twenty-four sputum negative cases of small pulmonary lesions smaller than 2 cm in diameter were studied. After thin-slide scanning and localization with Somatom DR-H computed tomorgraphy, the pulmonary nodules were biopsied with a 20 Gauge needle guided by a ruler especially designed. Biopsy materials were used for cyto- and histopathologic examination. The diagnosis accuracy of biopsy was evaluated by the result of postoperative pathology and/or observation for 2 years. RESULTS Sixteen pulmonary lesions were proved to be malignant and 8 benign. The sensitivity rate was 75.0% (12/16), specitivity rate 8/8 and accuracy rate 83.3% (20/24) according to cytopathology and 87.5% (14/16), 8/8, 91.7% (22/24) by histopathology, respectively. Two cases of early-stage peripheral lung cancer were detected and proved by operation. CONCLUSIONS CT-guided PTFNAB is safe and quick for diagnosis with high accuracy for small peripheral pulmonary lesions which are usually negative in sputum examination and bronchoscopy. PTFNAB should be widely used as routine in the diagnosis of lung neoplasms.