Viral croup is the most common form of upper airway obstruction in children 6 months to 6 years of age. It typically presents in the late fall or early winter, is often preceded by an upper respiratory infection, and is characterized by a low-grade fever, barking cough, and inspiratory stridor. Diagnosis is made on clinical grounds with no specific confirmatory test. The differential diagnosis of croup, including epiglottitis and retropharyngeal abscess, must always be considered in evaluating children with inspiratory stridor. Three therapeutic modalities are available for the treatment of croup: humidified air, racemic epinephrine, and adrenal corticosteroids. Maintaining at least 50% relative humidity in the child's room is recommended. If there is evidence of hypoxemia, a mist tent with supplemental oxygen may be helpful. Racemic epinephrine administered by nebulizer can quickly reverse airway obstruction in children with croup. The patient needs to be monitored for rebound airway obstruction for at least 2 hours after administration. The mainstay of treatment for severe croup is dexamethasone, administered 0.6 mg/kg, intramuscularly (IM). Dexamethasone is effective at decreasing the obstructive symptoms of croup, but its onset of action is approximately 6 hours after administration. Therefore, administration of racemic epinephrine is often helpful until the steroids begin to take effect. The correct dosage of dexamethasone is important, as lower steroid dosages have proven to be ineffective in treating croup. Dexamethasone IM, or an equivalent dose of oral prednisone, may be considered in children with moderately severe croup who do not require hospitalization.