The primary purpose of this study is to track patient outcomes for bilateral cochlear implant recipients in a cohort of 60 children, ages 12 to 36 months at time of surgery, who receive two implants in the same operation or in two different surgeries with the initial fitting of the devices separated by no more than six months.

Inclusion Criteria:

• Profound bilateral hearing loss
• Have independently elected to undergo bilateral implantation of Advanced Bionics HiResolution Bionic Ear System
• Age at implant: 12-36 months
• No previous cochlear implant use
• English as the primary language spoken in the home
• Parental willingness to follow study protocol

Exclusion Criteria:

• Deafness secondary to meningitis
• Presence of other conditions that could affect study participation