This chapter discusses the most significant and in some cases, only 'treatment' available for a child with a severe sensori-neural hearing-impairment: the provision of hearing-aids. In a normal ear the sound travels down the ear canal, through the eardrum and across the middle-ear cavity. Any obstacle or blockage in the outer ear may cause conductive hearing problems. The axis across the top of the audiogram represents the normal frequency range of sounds from low to high pitch. There are some sensori-neural hearing problems, such as a high-frequency loss, which may only come to light much later, perhaps when the child's hearing is screened in school. Meningitis is probably the commonest post-natal cause of deafness in young children. The sooner a hearing loss is discovered, the sooner something can be done to help reduce the impact of deafness at source.