Open operation for recurrent pneumothorax may be necessary to resect or oversew a bulla. At the same time, to stimulate adhesions, the pleura may be abraded with gauze, chemicals used to cause inflammation or a partial pleurectomy performed. Operation is necessary to decorticate the lung if it has developed a thick peel, in the presence of gross bleeding (hemopneumothorax) or if a large bulla is present. Occasionally, a chronic pneumothorax is due to a persistent leak caused by an adhesion holding open a bulla. The adhesion may be cut at thoracoscopy, using diathermy, and the leak will close. Many chemical agents have been used to encourage adhesions: iodized talcum powder, silver nitrate, 50% glucose and water, Atabrine, nitrogen mustard and tetracycline. In this series, one to three instillations each of 50 ml of autologous blood were used after the lung was fully expanded, usually after the use of an apical chest tube. This procedure was successful in 21 (85%) of 25 patients with difficult, chronic or recurrent pneumothoraces. It is a practical and easy method of causing a chemical pleurodesis, without serious side effects.