Attachment of bacteria to nonciliated cells of the nasopharyngeal epithelium was evaluated by immunofluorescence assay in 25 otitis-prone and 25 non-otitis-prone children undergoing ear, nose, or throat surgery under general anesthesia. The bacterial findings were analyzed simultaneously, both qualitatively and quantitatively. In otitis-prone children, there was a significant preponderance of epithelial cells having greater than 50 attached bacteria (P less than .001) and of epithelial cells with attached Streptococcus pneumoniae and Haemophilus influenzae (P less than .05). Also, the occurrence of Branhamella catarrhalis in the nasopharynx was more pronounced in the otitis-prone group (P less than .05). No significant differences in the occurrence of other middle ear pathogens or quantitative dominance of pathogens were noted between the two groups. Abundant attachment of pathogens to the epithelial cells close to the nasopharyngeal orifice of the eustachian tube is of a significant factor for the development of the otitis-prone condition.