Seventy-four children were enrolled in a double-blind placebo-controlled study to define the outcome of nonsuppurative otitis media with effusion (OME) over a 12-week period. Participants were randomly assigned to one of three treatment groups: pseudoephedrine (4 mg/kg/day), chlorpheniramine (0.35 mg/kg/day), or placebo. The children were reexamined at 2, 4, 8, and 12 weeks after enrollment unless earlier dismissed from the study because OME resolved or acute suppurative otitis media developed. Of the 66 children completing the study protocol, 44 percent had resolved OME, 38 percent developed acute suppurative otitis media, 14 percent had unresolved OME, and 4 percent developed severe hearing loss or medication side effects by the end of 12 weeks. The greatest incidence of both suppurative otitis media and resolution of OME occurred by 2 weeks of follow-up. There was no significant difference in resolution of effusion between treatment groups. Children who were 18 months of age or older with unilateral effusion had the best likelihood of resolution.