Purpose. The number of lung cancer patients is increasing in association with the aging of society, and age is associated with the risk of undergoing a thoracotomy procedure. We prospectively investigated the effi cacy of a functional operability algorithm that included pulmonary function and exercise test results for determining the indication for surgery in octogenarians. Methods. From April 2001 to October 2008, surgical indications for a total of 45 octogenarians were assessed using our algorithm, including forced expiratory volume in 1 s/forced vital capacity ratio, predicted postoperative percent of forced expiratory volume in 1 s, Hugh-Jones dyspneic index, and empirical anaerobic threshold obtained during an exercise test. Then the surgical results were reviewed. Results. Thoracotomy was contraindicated in one patient; the remaining 44 patients underwent surgery. Axilloanterior thoracotomy (75%), lobectomy (84%), and mediastinal lymph node dissection (73%) were the major procedures. Altogether, 37 postthoracotomy complications occurred in 29 (65.9%) patients. The 30-day and hospital mortality rates were 2.3% and 4.5%, respectively, and overall and disease-specifi c 5-year survival rates for the 42 patients were 54.5% and 79.6%, respectively. Conclusion. Following careful selection with our functional operability algorithm, octogenarians were able to tolerate a standard lung resection for primary lung cancer with acceptable morbidity and mortality. Their survival was consistent with that of younger cancer patients.