Forty-six patients with bullous emphysema were operated on. Respiratory function was investigated before and immediately after surgery, and during the follow-up to five years. The larger the volume of the bullae, the less disturbances of lung function caused by their removal immediately after operation. Respiratory function improved significantly during the long-term follow-up after removal of the bullae that were more than one third of the hemithorax, but it did not change when the bullae were less than one third of the hemithorax and deteriorated after pulmonary resection for the bullae associated with long-term pneumonia. No new bullae were revealed roentgenographically at five years postoperatively.