Two different otological noxes add up in their effect. In some cases, however, the first one may cause a reduction of the noxious effect of the second one. Opinions are divided as to whether the susceptibility to noise of an ear with chronic otitis media is increased or decreased. From 14,300 audiograms we selected those 131 cases with unilateral chronic otitis media and, at the same time, with a typical noise-induced recruitment-positive c5-dip on the other side. There were 86 cases with larger bone conduction hearing loss on the ear with chronic otitis media. In these cases, the bone conduction hearing loss, by all differential diagnostic criteria, could be judged to be caused by the chronic otitis media. On the other hand, in all those 45 cases which, on the side with chronic otitis media, had a bone conduction loss in form of a c5-dip, this was in each single case less pronounced than on the other ear. Regarding the susceptibility to noise, the reduction of sound intensity by the conductive deafness seems to be more important than noxious effects of the chronic otitis. Generally a substantial bone conduction hearing loss with chronic otitis media and noise exposure should be attributed to effects of the otitis.