Pulmonary Langerhans cell histiocytosis (PLCH) is a smoking-related interstitial lung disease characterized by development of cystic changes that predispose to occurrence of pneumothorax. To determine the frequency, recurrence rate, and optimal management of pneumothorax associated with PLCH. Retrospective study. Tertiary care, referral medical center. One hundred two adults >or= 18 years old with histologically confirmed PLCH seen at Mayo Clinic Rochester over a 23-year period from 1976 to 1998. None. Sixteen of 102 patients (16%) with PLCH had pneumothorax; mean age at the time of diagnosis was 29.4 years (range, 18 to 52 years), and all had smoked cigarettes. There were 37 episodes of pneumothoraces (1 to 5 episodes per patient); 10 patients (63%) had more than one episode. Median age at diagnosis of PLCH was significantly younger in patients with pneumothorax when compared to those without pneumothorax (27 years vs 41.5 years, p < 0.001), but pulmonary function parameters and survival after diagnosis were not significantly different. Rate of recurrent pneumothorax was 58% to the ipsilateral side when the episode was managed by observation or chest tube without pleurodesis, and 0% after surgical management with pleurodesis. These data support the early use of surgical therapy with pleurodesis in managing patients with PLCH and spontaneous pneumothorax.