Objective: To determine the added clinical benefit of nebulized budesonide in children with mild to moderate croup treated with 0.6 mg/kg oral dexamethasone., Design: Randomized, double-blind, placebo-controlled trial., Setting: Emergency department of a tertiary-care pediatric hospital with 47,000 visits per year., Participants: Children 3 months to 5 years of age with a syndrome consisting of hoarseness, inspiratory stridor, and barking cough and a croup score of 3 or greater after at least 15 minutes of mist therapy. Patients were excluded from the study if they had diagnoses of epiglottitis, chronic upper or lower airway disease (not including asthma), or severe croup or had received corticosteroids within the preceding 2 weeks., Intervention: All patients received 0.6 mg/kg oral dexamethasone and were randomly assigned to receive 4 mL (2 mg) of budesonide solution (n=25) or 4 mL of 0.9% saline solution (n=25) by updraft nebulizer with a continuous flow of oxygen at 5 to 6 L/min., Main Outcome Measures: The primary outcome measure was the proportion of patients in each group who had clinically important changes (two points) in the croup score during the 4 hours after treatment., Results: Eighty-four percent (n=21) of the patients who received budesonide had clinically important responses, compared with 56% (n=14) in the placebo group. The number of patients who would need to be treated with nebulized budesonide for one patient to have a clinically important response is four patients., Conclusions: Despite receiving simultaneous oral dexamethasone, pediatric outpatients with mild to moderate croup have added, clinically important improvement in respiratory symptoms after treatment with budesonide.