Introduction: Otosclerosis is an osteodystrophy of the labyrinthine capsule producing conductive hearing loss. If the process invades the cochlea, a sensorineural hearing loss usually takes place. The cochlear implant is a good alternative in these patients. Objective: To ascertain the behaviour of cochlear implantation in otosclerosis. Material and methods: We reviewed a database of 250 patients that underwent cochlear implantation, performing a retrospective study of 13 patients with clinical, audiological and/or imaging findings of bilateral otosclerosis. The 26 ears were studied as to their natural history, previous surgeries, evolution to profound hearing loss, computed tomography images, complications and functional results. Results: Of the cases studied, 46% were female and 54% were men, with a mean age of 26 years at the onset of conductive hearing loss. Stapes surgery was performed in 19 ears (73%), with a mean patient age of 29 years, and 53% of them underwent cochlear implantation. Computed tomography results showed that there were signs of different degrees of radiological affectation in 54% of the ears. A total of 3 complications took place (23%): implant failure, overstimulation of the facial nerve and bilateral tinnitus were found. One year after implantation, the average percentages of correct 2-syllable words were 80% and 85% in open sentences. Conclusions: Patients having profound bilateral sensorineural hearing loss secondary to otosclerosis obtain great benefit from cochlear implantation. (C) 2011 Elsevier Espana, S.L. All rights reserved.