A prospective cross-sectional study was done to investigate the involvement of middle ear disease in cystic fibrosis. Eighty-eight patients with cystic fibrosis, aged 1-28 years, were examined during the winter period 1995-1996 at regular follow-up visits to detect history and prevalence of inflammatory and infectious middle ear disease by questionnaire, otoscopy and tympanometry. One third of the patients had a history of otitis media, but only in 9% did this occur more than once. Hearing problems were recorded in 8%, but this was severe in only one case. Otoscopy showed 141 normal tympanic membranes, 17 times retraction, 15 times otitis media with effusion, once an acute otitis media in both ears. Only one patient had a grommet in one ear. More than 70% of the tympanograms were normal. A flat curve, type B according to Jerger's classification, was found in 11 ears. The youngest age group had a higher prevalence of abnormal findings on otoscopy and tympanometry, while patients who had undergone paranasal sinus surgery had less frequently abnormal findings. In conclusion, no evidence that cystic fibrosis is associated with increased prevalence of middle ear disease has been found in this prospective cross-sectional study.