Simple spirometric testing remains useful for the preoperative assessment of patients being evaluated for thoracotomy. To routine spirometric testing, the maximal voluntary ventilation should be added. More specific tests do not seem to add predictive information. In addition, individual tests do not seem to correlate with specific complications. The amount of lung resected does not correlate with the occurrence of complications. Patients undergoing lobectomy as opposed to pneumonectomy often experience a stormy postoperative course and are prone to have atelectasis develop and to have an infection in the lung remaining on the operated upon side. Recent data would indicate that this remaining lung tissue is severely compromised during the immediate postoperative period. Those patients who undergo lobectomy may transiently lose considerably more function than would certainly be anticipated from the amount of tissue resected.