Multiple large and small emphysematous bullae were resected in 27 patients with chronic obstructive lung disease (COLD). Twenty-two patients were operated on one side, and 5 patients underwent bilateral consecutive Operations. Twentyfive patients were male, 2 female, and they were between 22 and 67 years old (mean 49.5 years). All patients had a follow-up examination between 3 and 48 months postoperatively. As operative techniques, resection by means of a clamp, plication of cysts according to Nissen, resection with homologous dura plasty (7 patients) and pericardial plasty (7 patients) were used, In 19 patients preoperative and postoperative pulmonary function was compared. Functional improvement occurred in 17 patients - including all of the 5 bilateral procedures. Postoperative improvement was more pronounced with decreasing preoperative pulmonary function, measured as VC, RV, IGV and Raw [ * ]. Partia pulmonary insufficiency could be improved in 9 patients and global pulmonary insufficiency was improved in 5. In 16 cases physical work capacity was increased. The hemodynamics of the pulmonary circulation were improved in all patients with increased preoperative pulmonary artery pressure (latent pulmonary hypertension in 7 patients, overt pulmonary hypertension in 5). FEV1 [ * ] was least influenced by surgery, especially in patients more tnan 50 years old. The long-term prognosis, thus has to be judged cautiously. One patient died postoperatively (mortality 4%). The technique of dura and pericardial plasty, aiming at functional adaptation, is described. Sutures inverting or folding pulmonary tissue are avoided. The aspect of at least temporary (up to 3 years) functional improvement ieads us to advocate the use of extended criteria of operability. 1 List of Abbreviations: VC = vital capacity; RV = residual volume; IGV =intrathoracic gas volume; Raw = airway resistance; FEV1 = forced expiratory 1-second-volume