Thirty-eight high-risk patients (forced expiratory volume in one second [FEV1] less than 2.0L or maximum voluntary ventilation [MVV] less than 50 per cent of predicted) were observed for a minimum of one year after pneumonectomy for carcinoma of the lung. Operability was assessed by calculating a predicted postoperative FEV1 (based on the right-left fractional perfusion estimated by a perfusion lung scan) and requiring this predicted postoperative value to exceed 800 ml. No other invasive physiologic studies were performed before surgery. At one year, 23 of 38 patients were still alive, and 13 of 38 patients survived to the end of the second year. At five years, two of 15 patients were alive with no evidence of metastatic disease. This simple physiologic approach involves widely available techniques and, in patients with lung cancer who have compromised pulmonary function, appears to result in acceptable survival over a longer period.