Otosclerosis is a multifactorial disease. A number of theories on the pathogenesis of this disease have been established in the last decades. It is important to review recent data on the pathogenesis of otosclerosis as it is a severe inner ear disease leading to deafness in the majority of cases. Surgical therapy is not always successful or feasible. In this review, authors describe the most relevant genetic, infective, immunological, inflammatory factors, as well as the impaired bone metabolism underlying the pathogenesis of otosclerosis. It is likely that genetic predisposition associated with morbilli infection may lead to bone resorption in the stapes and cochlea followed by spongiosis, fibrosis and sclerosis. It has been suggested that immunological mechanisms play a central role in the development of the disease. Some authors consider otosclerosis as autoimmune disorder based on the presence of several autoantibodies. Apart from classical diagnostic methods, such as audiometry and X-ray, novel radiological techniques including CT, MRI or radionuclide scan are helpful in the localization of otosclerosis. As surgery is sometimes contraindicated or unsuccessful, drug therapy including the use of anti-osteoporotic on non-steroidal antiinflammatory drugs may be administered, especially in the early phase of the disease.