Percutaneous transthoracic needle biopsy (TNB) is a simple and safe procedure with high diagnostic accuracy for the diagnosis and staging of cancer in the lung, hilum, and mediastinum. The complication rate is low and consists primarily of pneumothorax, with only a small percentage of these requiring chest tube reexpansion. Major complications are rare. Computed tomographically guided biopsy is a powerful adjunct to fluoroscopic biopsy and expands the application of TNB to include most thoracic lesions. TNB is the initial diagnostic procedure of choice in peripheral lung lesions, suspected focal metastases, and most hilar and mediastinal masses. Its proper role in the diagnosis and staging of lung cancer requires the close collaboration of the radiologist, cytopathologist, and the patient's primary physician.