Stridor is a sign of upper airway obstruction. In children, laryngomalacia is the most common cause of chronic stridor, while croup is the most common cause of acute stridor. Generally, an inspiratory stridor suggests airway obstruction above the glottis while an expiratory stridor is indicative of obstruction in the lower trachea. A biphasic stridor suggests a glottic or subglottic lesion. Laryngeal lesions often result in voice changes. A child with extrinsic airway obstruction usually hyperextends the neck. The airway should be established immediately in children with severe respiratory distress. Treatment of stridor should be directed at the underlying cause.