The acute onset of stridor in a young child usually represents viral croup, particularly during the fall and early winter. If the clinical picture is entirely consistent with this diagnosis and gas exchange is maintained, management with cool mist at home is appropriate. Rapid deterioration is unusual in viral croup; however, if obstruction is prolonged or becomes unusually severe, racemic epinephrine aerosols, hospitalization for careful observation, a brief course of corticosteroid therapy, and, rarely, endotracheal intubation may be required. Many of the other causes of acute stridor in childhood represent true pediatric emergencies: epiglottitis, foreign body aspiration, bacterial tracheitis, allergic airway edema, and retropharyngeal abscess, all requiring management with a consultant. Chronic stridor in infancy most often represents laryngomalacia, a developmental abnormality of the laryngeal cartilage which usually resolves by the second year of life and rarely requires specific treatment. Other causes of chronic stridor in childhood include subglottic hemangioma, vocal cord paralysis, and a long list of abnormalities. In the older child with chronic stridor or in the infant whose clinical picture is unusual for laryngomalacia, airway roentgenograms, barium studies, or laryngoscopy/bronchoscopy should be obtained to establish the definitive diagnosis.