Between July 1985 and March 1992, 20 children received either heart-lung (11), double lung (8), or single lung (1) transplants at our center. Since 1988, flexible fiberoptic bronchoscopy with bronchoalveolar lavage and transbronchial biopsy have been carried out to monitor for rejection or infection in these patients. As of March 31, 1992, we have performed a total of 112 transbronchial biopsies in our patients, who ranged from 6.8 to 18 years of age and 19.3 to 67.3 kg in weight. All but two of these procedures were carried out using conscious sedation and a transnasal approach. Four to seven biopsy samples were obtained at each procedure. One patient had hemorrhage (< 100 ml) and no patient had pneumothorax as a complication. Of the biopsy samples, 72.4 percent had a surface area of greater than 2 mm2, and 89.5 percent of the biopsy samples were deemed adequate for pathologic interpretation. We believe that for the majority of pediatric lung or heart-lung recipients, flexible bronchoscopy and transbronchial biopsy using conscious sedation and a transnasal approach is safe and permits the recovery of adequate tissue for pathologic evaluation. The avoidance of general anesthesia, endotracheal intubation, and mechanical ventilation at the time of bronchoscopy and transbronchial biopsy probably decreases the likelihood of pneumothorax as a complication of the procedure.