The aim of this study was to determine if 2 doses of oral dexamethasone are as effective as a 5-day course of oral prednisone in preventing relapse for pediatric asthma exacerbations. Patients presenting to the emergency department with an asthma exacerbation were randomized to receive 0.6 mg/kg of dexamethasone or 2 mg/kg of prednisone in a prospective, double-blind study. The primary outcome was relapse within 10 days, and the secondary outcome was vomiting in the emergency department. Eighty-nine patients completed the study: 38 in the prednisone group and 51 in the dexamethasone group. In all, 3 patients in the prednisone group (8%) and 8 patients in the dexamethasone group (16%) required an unscheduled follow-up visit (P = .27). In all, 7 patients in the prednisone group (18%) and 5 patients in the dexamethasone group (10%) had vomiting ( P = .24). No difference was found in the relapse rate or incidence of vomiting between patients given prednisone and dexamethasone for pediatric asthma exacerbations.