Recent progress in the medical field have restored a level of hearing to people with a certain level of hearing impairment that was impossible to correct with conventional hearing aids. To date, 80 000 people in the world have benefited from the cochlear implant technique. The cochlear implant is recommended for people with deafness in both ears, from profound to total deafness, for whom hearing devices have not produced a sufficient level of speech intelligibility. This system is indicated for adults who have lost their hearing following an illness, poisoning, head injury or natural ageing of the ear. It also concerns children who lost their hearing at birth or in the first few years. Whether it be a child or an adult, it is important to take advantage of the cochlear implant as soon as possible. The longer the period of deafness, the more the brain loses its capacity to hear and nerve endings change making re-education harder. It is even more urgent in young children because the lack of exposure to sound causes brain atrophy. It is then essential to carry out the implant as soon as possible from the age of two years. People who have been deaf for a long time, adult, or adolescent, obtain less convincing results but may still benefit from a cochlear implant.