Croup is a common childhood respiratory illness with peak incidence in October and November. Inflammation of the subglottic structures results in obstruction of the upper airway, causing the characteristic barking cough, hoarseness, and inspiratory stridor. Fever may also be present. Patients with suspected croup should be assessed for more severe causes of upper airway obstruction, such as bacterial tracheitis, retropharyngeal abscess, peritonsillar abscess, foreign body obstruction, and epiglottitis. Radiography or laboratory testing is typically unnecessary for diagnosis but should be considered if the diagnosis is unclear. Corticosteroids are recommended as first-line treatment to reduce symptom burden and the need for advanced medical care. Dexamethasone is the most-studied corticosteroid, but prednisolone may also be used. A single oral dose of dexamethasone (0.6 mg/kg, maximum 12 mg) is standard. Moderate to severe croup should be treated with nebulized epinephrine and corticosteroids. Recurrent episodes of croup should prompt evaluation for an underlying anatomic abnormality or medical condition.