Background: Thoracoscopy has been accepted as a technique in pediatric surgery for diagnosis of thoracic pathology, but there has been little experience using it as a therapeutic modality as well. The purpose of this report is to describe and critically evaluate a 7-year experience with thoracoscopic diagnosis and resection of mediastinal masses in infants and children. Methods: From February 1993 to June 2000, 39 patients presented with mediastinal masses and no tissue diagnosis. Age ranged from 5 months to 18 years old and weight from 3.6 to 110 kg. Twelve children had anterior mediastinal masses, 27 posterior. The patients were positioned in a modified prone or supine position, and single lung ventilation was performed on the contralateral side. Three or 4 valved trocars were utilized with 3 and 5 mm instrumentation. Results: A total of 38 of 39 procedures were completed successfully endoscopically. The procedure in 1 patient with a sarcoma was converted to thoracotomy because of extensive disease. Operating times ranged from 20 to 185 minutes. Diagnosis was obtained in all cases, and complete excision was performed in 33. All children were extubated in the operating room; 8 chest tubes were placed but removed within 24 hours. Hospital stay ranged from 12 hours to 4 days. Pathology included 12 foregut duplications, 7 ganglioneuromas, 6 neuroblastomas, 6 lymphomas, 3 teratomas, 2 sarcomas, and 3 other lesions. Conclusion: Thoracoscopy is a safe and effective method to evaluate, biopsy, and in most cases resect lesions of the anterior and posterior mediastinum in infants and children. J Pediatr Surg 36:1165-1167. Copyright (C) 2001 by W.B. Saunders Company.