It has been suggested that asymmetric or fluctuating hearing in otitis media with effusion (OME) could lead to abnormal binaural hearing. In a cohort of children with tympanogram data obtained at 3-monthly intervals from 2 to 4 years, 6.4% had asymmetric or unilateral B tympanograms on more than half the test occasions, or had 5 or more fluctuations between symmetric and asymmetric tympanograms. Hence there are sufficient cases for studies of sequelae or treatment in unilateral and fluctuating OME. Few of these cases would have received medical attention under a bilateral referral criterion.