CROUP, or acute laryngotracheobronchitis, is the most common cause of upper airway obstruction in children. In this study, the efficacies of intramuscular and oral DEXAMETHASONE administration are compared for treatment of CROUP. This is a single-blind randomized trial involving 68 children divided into two groups, the first group received 0.6 mg/kg intramuscular DEXAMETHASONE and the second group received 0.6 mg/kg oral DEXAMETHASONE. The clinical score, respiratory rate, heart rate, O2 saturation and clinical response were assessed before and then hourly for four hours after treatment. The respiratory rate of two groups was significantly different at the first hour of treatment (P= 0.02), but it did not vary between study groups at the second, third, and fourth hour of treatment. There was no statistical difference among clinical score, heart rate, O2 saturation and clinical response in any of the measurement times. Oral and intramuscular administrations have the same effectiveness for treatment of CROUP and oral DEXAMETHASONE was proposed because this is a non-invasive procedure.