According to the 2012 annual report of the Japanese Association for Thoracic Surgery, the total number of surgical procedures performed for the treatment of lung cancer had reached 35,667. Patients over 70 years of age comprised 52% of those surgical cases, and those over 80 years 12%. This tendency has been increasing annually. Although hospital mortality rates in elderly patients over 80 years of age and others were almost the same, 30% of elderly patients died from other diseases, as reported by the Japanese Joint Committee of the Lung Cancer Registry in 1999. Therefore, current preoperative physiological and oncological risk evaluations of elderly patients do not appear to be sufficient. The Japanese Association for Chest Surgery planned and performed a multiinstitutional prospective cohort study of elderly patients with lung cancer who underwent thoracic surgery to answer clinical questions surrounding such risk evaluations.