Seventy-two children hospitalized for croup received on admission a single dose of either 0.6 mg/kg dexamethasone or an equivalent placebo intramuscularly from randomized ampules; subsequently the same patients were randomized to receive either nebulized racemic epinephrine or saline by intermittent positive pressure breathing. Of the four treatment groups those receiving a placebo injection and nebulized saline had the slowest recovery by all criteria. Dexamethasone and nebulized epinephrine reduced the symptoms and hastened recovery, but dexamethasone was more effective by clinical evaluation at 6 and 12 hours post admission. The patients given dexamethasone had a significantly shorter hospital stay than those receiving placebo. We conclude that a single injection of a potent corticosteroid is beneficial in acute spasmodic croup. Nebulized racemic epinephrine given with an appropriate device is also effective, but the effect of epinephrine is less remarkable in patients treated with dexamethasone.