A retrospective analysis has been undertaken of 53 operations in 42 patients with severe chronic obstructive airway disease. All patients had a forced expiratory volume in 1 second between 0.3 and 1 litre, but the outcome of surgery was successful after their first operations, all of which were elective; 38 of the 42 had uneventful anaesthesia and surgery together with a normal postoperative period, while four had artificial ventilation of the lungs. The best predictors of the use of postoperative ventilation were the arterial PO2 and whether the patient was dyspnoeic at rest.