Stridor is the sound caused by abnormal air passage during breathing. The cause of stridor can be located anywhere in extrathoracic airway (nose, pharynx, larynx, and trachea) or the intrathoracic airway (tracheobronchial tree). Stridor may be acute (caused by inflammation/infection or foreign body inhalation) or chronic. It may be congenital or acquired. Stridor is a sign from which the underlying cause must be sought; it is not a diagnosis. The role of the pediatrician faced with a child or infant with noisy breathing is: (1) to determine the severity or respiratory compromise and the need for immediate intervention (to prevent respiratory failure); (2) to decide based upon history and clinical examination whether a significant lesion is suspected and, in the latter situation, to refer the child to an ENT surgeon for an upper and lower airway endoscopy; (3) to understand the consequences and management strategies of the underlying lesion and to collaborate with colleagues from related disciplines for follow-up and subsequent management of the child.