Nine hundred sixty-one patients underwent operations for the treatment of carcinoma of the lung; 18 percent of these were 70 years of age or older. The effect of various factors, singly or in combination, on the incidence of postoperative complications was assessed. Variables included age, sex, cardiopulmonary status, cell type, stage of the disease, and type of procedure performed. The postoperative course was uneventful in 81 percent of the patients; 8 percent had minor complications, 9 percent major complications and 2 percent died. The majority of the complications were cardiorespiratory. High risk factors were identified to be old age, restricted cardiopulmonary reserve, and the need for pneumonectomy. The low incidence of mortality and major morbidity observed was attributed to careful preoperative evaluation, selection of the appropriate surgical procedure, and inclusion of routine preoperative physiotherapy in all patients.