An inflammatory process in the middle ear caused by bacteria or bacterial products emanating from the nasopharynx is one etiological factor considered in the unknown pathogenesis of otitis media with effusion (OME). The nasopharyngeal prevalence of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella (Branhamella) catarrhalis and Streptococcus pyogenes was studied in 191 children with defined OME and in 53 age-matched children without middle ear disease. Duplicate sampling and semiquantitative analysis were performed to assess even minor differences in the distribution of pathogens between the two groups of children. Pathogens were recovered in 91% of OME children. A significantly higher number of pathogen species/patient (1.66 vs. 1.15, p less than 0.01) as well as pathogen colonies/patient was found in OME children compared to control children. Chronic OME in children is associated with an increased pathogen load in the nasopharynx, suggesting a role of these pathogens in the etiology of OME.