The contribution of percutaneous fine needle aspiration biopsy of the lung to the diagnosis of lung lesions has been evaluated. Between 1976 and 1981 this method was used in 600 patients of the Research Institute of Tuberculosis and Respiratory Diseases. In 72 patients the diagnosis was not clearly confirmed during the follow-up period. Lung biopsy contributed to the diagnosis in 458 (88.7%) out of the remaining 528 patients. The main contribution of this method was in the examination of patients with malignancies. Of the 421 cases of malignant neoplasm, the cytological finding correlated with the definitive diagnosis in 88% of cases. False negative finding was in 11.3% and false positive in 0.7% of cases. In the discussion the possibilities of cytological examination as well as the causes of some errors are analyzed. The technique applied, indications and contraindications of this procedure as well as its complications are reported, indications and contraindications of this procedure as well as its complications are reported. Pneumothorax occurred in 21.2% of patients; in most cases it was only a small one. A pneumothorax requiring chest tube drainage or exsufflation occurred in 7% of cases. Small haemoptysis in 1.4% and there were no other complications.