Cochlear implant surgery in three dogs and one cat. Cochlear implantation was carried out in 3 dogs and 1 cat. Surgery in all cases was performed by the cochlear fenestration method, in which a fenestration was made in the promontory and the apex. Cochlear implant electrodes were inserted by the facial recess approach. The devices used were a Nucleus 24M receiver-stimulator, a Digisonic and a Symphonie II for the dog. This procedure did not give good results because of the small size of the canal. The surgical procedure was easy to perform and no long-lasting complications were encountered. The cochlear fenestration technique may be a good method for cochlear implantation in dogs and cats. The indications and limitations are still unclear and further investigation is needed to determine if it will be a feasible option for cochlear implantation in pet dogs and cats.