Congenital stridor was observed in a newborn due to left pulmonary artery sling. Clinical signs and the course of the disease were determined by an extreme tracheal stenosis. In newborns and infants with apneic episodes, inspiratory and expiratory wheezing and cyanosis a pulmonary sling should be considered. Unilateral hyperexpansion of the lung and an anterior indentation of the esophagus are helpful diagnostic signs. Surgical treatment for pulmonary sling is possible but remains unsatisfactory. Patients with associated tracheobronchial stenosis show a high over-all mortality rate.