Laryngeal infection in childhood causes airway obstruction, of which the cardinal symptom is stridor. In the developed world, ‘croup’ – a clinical scenario characterized by a combination of stridor hoarseness and a typical barking cough – is the commonest (90%) cause of acute airway obstruction in children. Epiglottitis has been the next most common infective cause but is now seen much less frequently due to the widespread introduction of Haemophilus influenzae b (Hib) vaccine; bacterial laryngotracheobronchitis and diphtheria are less common. The differential diagnosis of acute acquired stridor includes ‘spasmodic croup’, retropharyngeal abscess, angioneurotic oedema, neoplasia, acute laryngeal trauma and foreign body aspiration.