PNEUMOTHORAX is a recognized complication of cystic fibrosis.1-3Although described as unusual3or rare,2the actual incidence of this complication has not been defined, nor has the clinical significance been assessed. Furthermore, the literature on this problem is presently restricted to single case reports,3-5with little opportunity for evaluation of treatment. In particular, there is no information on the management of persistent or recurrent pneumothorax complicating cystic fibrosis. It is the purpose of this paper to review our experience with 20 cases of cystic fibrosis and pneumothorax, and to present four cases in which open thoracotomy and direct surgical intervention were required because of persistent or recurrent pneumothorax. Subjects and Methods The records of all patients with cystic fibrosis seen at Babies Hospital, Columbia-Presbyterian Medical Center, New York, from January 1953 through December 1967 were reviewed. Of a total 710 patients seen over this 15-year period,