Otosclerosis is one of the most common causes of acquired hearing loss. The incidence of otosclerosis of 2.5% seems to be the same for most populations and with no difference between the sexes. However, the incidence of clinical otosclerosis (causing hearing impairment that requires stapedectomy surgery, a hearing aid or in very extreme cases, a cochlear implant) is much lower and differs between different ethnic groups, races and the genders. It is rare in Africans, Orientals and South Americans, and more frequent in populations of European origin where the prevalence is about 0.4%. It is more frequent in women with a female to male ratio of 2:1. In about 85% of people with clinical otosclerosis the hearing loss is bilateral with the remainder having hearing loss in only one ear. The familial nature of clinical otosclerosis was first reported in 1861. A twin study reported in 1966 found the presence of clinical otosclerosis in nearly all 40 pairs of identical twins, supporting the early hypotheses that otosclerosis had a genetic basis. Numerous studies on families with otosclerosis suggested that the pattern of inherence was autosomal dominant (meaning you only need to get the abnormal gene from one parent in order for you to inherit the condition). But with the proportion of individuals carrying the abnormal gene ranging from 25-40% the impression was given that hearing loss in otosclerotic families might skip a generation. Although a strong family history exists in many patients with otosclerotic hearing loss, about 40-50% of cases are sporadic with no family history. When all past and new data concerning the occurrence of clinical otosclerosis is examined, it seems like the genetic basis of the disease is complex and the expression of the associated hearing loss is dependent on multiple factors including those in the environment (oestrogens, fluoride, viral infections). Studies are underway to shed light on the genetic base diseases that are associated with hearing loss and the various forms of inheritance that lead to both histological and clinical otosclerosis. Hopefully this will allow individuals, families and their treating doctors to further understand the risk to both this generation and their children of developing otosclerotic hearing loss in one or both of their ears.