To determine whether the adjunctive drugs antihistamine and corticosteroid improve immediate and long-term outcomes of acute otitis media (AOM).Children with AOM (3 mos-6 y) were enrolled in a randomized, double-blind, placebo-controlled trial. All 179 children received one dose of intramuscular ceftriaxone and were assigned to receive either chlorpheniramine maleate (0.35 mg/kg/d) and/or prednisolone (2 mg/kg/day) or placebo for 5 days. Main outcome measures were rate of treatment failure during the first 2 weeks, duration of middle ear effusion, and rate of recurrences of AOM to 6 months.Clinical outcomes and recurrence rates did not differ significantly with treatment. Children who received antihistamine alone had significantly longer duration of middle ear effusion (median, 73 days) than subjects in other treatment groups (median, 23 to 36 days, P=.04). Temporary normalization of tympanometric findings on day 5 occurred more frequently in the corticosteroid-treated group (P=.04).Five-day treatment with antihistamine or corticosteroid, in addition to antibiotic, did not improve AOM outcomes. Antihistamine use during an acute episode of OM should be avoided, since the drug may prolong the duration of middle ear effusion. The efficacy of 7- to 10-day treatment of AOM with corticosteroid, in addition to antibiotic, deserves further investigation.