The exploratory cochleotomy is a new diagnostic procedure for the selection of cochlear implant candidates. We use this procedure to assess the excitability of the auditory nerve, the patency of the cochlea and to detect undesirable side effects of electrical stimulation, such as facial nerve activation. The exploratory cochleotomy is a limited surgical procedure performed under local anesthesia in adults and light sedation in children. It is combined with the recording of electrically evoked brainstem responses elicited by an intracochlear probe electrode.