In the past 10 years two children, ages 3 1/2 and 7 years, have been seen with central endobronchial fibrous histiocytoma causing complete atelectasis. Each child had a 4- to 6-month history of cough, dyspnea and fever. After antibiotic failure, x-rays demonstrated complete unilateral lung collapse. Bronchoscopy in case 1 demonstrated total occlusion of the left mainstem bronchus with 80% stenosis of the right. Left pneumonectomy was ultimately performed with removal of tumor frm the right bronchus. Ten years later the patient is well. Case 2 had an extrinsic etiology ruled out by computed tomography scan. Ventilation/perfusion scan showed no ventilation and only faint perfusion of the involved lung. Pulmonary function testing showed moderate to severe restrictive changes with air trapping. Total obliteration of the left mainstem with tumor projecting into the carina was observed on bronchoscopy. Endoscopic resection was not felt to be safe. Thoracotomy showed a totally atelectatic, edematous lung filled with pus. The left main bronchus was opened, the tumor removed, and the distal bronchus lavaged and selectively ventilated. Partial lung expansion was obtained. The child is well 1 1/2 years later with a normal chest radiograph, pulmonary function tests, and bronchoscopy. Fibrous histiocytomas of the lung, if in a central endobronchial location, can cause complete lung collapse. A combination of tumor resection, lavage, and selective ventilation should be attempted as an alternative to pneumonectomy, even if the lung appears to be nonsalvageable.