The etiology of middle ear disease in Nijmegen, The Netherlands was studied on the basis of a data set collected in a prospective epidemiological study on otitis media with effusion (OME) in a cohort of 1439 preschool children. A factor analysis was used to evaluate two hypotheses: (1) that OME, acute otitis media (AOM), common cold and tonsillitis are manifestations of the same pathological entity, and (2) that a group of children can be distinguished who develop these conditions more frequently than average. The results only partly supported these hypotheses. The correlation between OME, AOM, common cold and tonsillitis was lower than expected from a review of the literature. Common cold appeared to be the ubiquitous ENT disease in childhood and, depending on the child's predisposition, could be accompanied by OME, AOM or tonsillitis. The course of middle ear and upper airway disease showed a gradual scale from "healthy" to "ill" with most of the children suffering from these conditions at an average frequency.