Gastroesophageal reflux is thought to be an important etiology of the various upper aerodigestive tract disease. To investigate the role of gastric acid and pepsin as an etiologic factor of laryngotracheal stenosis, and the difference of injury by synthetic gastric juice between in ciliated respiratory epithelium and in squamous epithelium, experimental study was carried out using rabbits. Mucociliary transport affected by synthetic gastric juice was also studied in dogs. Synthetic gastric juice of low pH caused serious damage and Impairment of mucociliary transport in the epithelium of the larynx and trachea. Gastric acid played major role in the mucosal damage. Squamous epithelium of vocal folds and pharynx was more resistant to synthetic gastric juice than respiratory epitheium. In conclusion, gastroesophageal reflux may be an etiologic factor in the developement of laryngotracheal stenosis, so the adequate management is necessory In patients of laryngotracheal stenosis.