Cochlear implantation has proven beneficial for numerous children with profound congenital hearing impairments. Some congenitally deaf ears, however, may have anatomical malformations. This study reports the authors' recent experience with cochlear implants in patients with cogenital inner ear malformations. Since 1987, 10 patients with congenital abnormal inner ear structures have been implanted at the House Ear Clinic; 8 with abnormal cochleas and 2 with enlarged vestibular aqueducts. Nine patients received the Nucleus 22 device and 1 patient was implanted with the 3M/House device. Some modifications of the routine surgical approach were required in 5 patients. A cerebrospinal fluid (CSF) leak occurred in 4 of the 10 cases. There was a relationship between the degree of abnormality and the number of electrodes that could be inserted. All 10 patients can perceive sound and are active users of their implants.