The problem of deafness or hearing loss is increasing world-wide. In countries rich and poor, people are living longer, and presbyacusis, the deafness of old age, is becoming more frequent. Hearing loss is a chronic and often life-long disability that, depending on the severity and the frequencies affected, can cause profound damage to the development of speech, language, and cognitive skills in children, especially if commencing prelingually. That damage, in turn, affects the child's progress in school and, later, his or her ability to obtain, keep, and perform an occupation. For all ages and for both sexes, hearing loss causes difficulties with interpersonal communication and leads to significant individual social problems, especially isolation and stigmatization. All of these difficulties are much magnified in developing countries, where there are generally limited services for the hard of hearing, few people trained to help those with hearing loss, and little awareness about how to deal with the difficulties associated with such loss. Although deafness and hearing impairment are likely to have huge economic effects in such countries, in most areas these effects remain to be quantified.