Purpose : Results of 181 percutaneous needle aspiration biopsies performed with an 18-gauge needle during aperiod of 3 years were analyzed to determine efficacy and safety of the procedure. Materials and Methods :Biposies were performed in patients that could not be diagnosed by bronchoscopy or sputum cytology. The biopsyprocedure with 18-gauge Crown needle was guided by fluoroscopy. The biopsy specimen placed in 10% formalinsolution were histologically confirmed. Results : In 160 patients (89%), the positive diagnosis was made bypercutaneous needle aspiration biopsy. There were 153 lung lesing (120 malignant and 33 benign lesions) and 7mediastinal lesions. the diagnostic accuracy of malignant and benign disease was 91% and 80% respectively.Complications included pneumothorax (n=11) and hemothorax (n=1):six of them required treatment with chest tube andthe remainder showed spontaneous resporption. Conclusion : PCNB with an 18-gauge needle provided a reliable,relatively safe diagnostic tool to establish the diagnosis of both malignant and benign chest lesions.