The otological characteristics of a birth cohort of 7.5-8-year-old Dutch children are reported. Questionnaire information was available for 1004 children, while otomicroscopic, tympanometric and pure-tone audiometric data were available for 946 children. Twenty-nine per cent of the children had been treated surgically for various ENT diseases. Fifty-five per cent of the children had normal tympanic membranes, 19% mild abnormalities, and 26% moderate to severe abnormalities. At this age the prevalence of bilateral otitis media with effusion (OME), as shown by a type B tympanogram was 2.5%, while that of unilateral OME was 7%. A pure-tone average hearing level of > or = 15 dB in the better-hearing ear was found in 4% of the children. The presence of OME was associated with a mean hearing loss of 20 dB. This study shows that structural and functional middle-ear abnormalities are highly prevalent in Dutch school children.