Chronic otitis media with effusion (OME) has been observed in 10 to 20% of children following acute, symptomatic otitis media. To determine factors that place children at increased risk of chronic OME, we conducted a 6-week prospective study of 386 children who had 3 or more recent episodes of otitis media and who had middle ear effusion present for at least 2 weeks. Of these children 23% developed chronic OME (i.e. effusion lasting 8 continuous weeks or more), and 26% developed chronic OME complicated by acute, symptomatic otitis media. Predictors for chronic OME were (1) bilateral OME, (2) duration of effusion for greater than 2 weeks at enrollment and (3) day care attendance. Children with these 3 factors had twice the risk of developing chronic OME as children lacking all 3 factors. These risk factors can be used to target children for early, aggressive OME therapy.