The incidence of autoimmune inner ear disease (AIED) is difficult to determine: probably it is a rare disease, accounting for <1% of all cases of hearing impairment or dizziness. Nevertheless, the diagnosis of AIED might be overlooked because of the lack of a specific diagnostic test. The hallmark of this clinically diagnosed condition is the presence of a rapidly progressive, often fluctuating, bilateral sensorineural hearing loss (SNHL) over a period of weeks to months. The progression of hearing loss is too rapid to be diagnostic for presbycusis and too slow to conclude a diagnosis of sudden SNHL. Vestibular symptoms, such as generalized imbalance, ataxia, positional vertigo and episodic vertigo may be present in almost 50% of patients. Occasionally only one ear is affected initially, but bilateral hearing loss occurs in most patients, with symmetric or asymmetric audiometric thresholds. Almost 25-50% of patients also have tinnitus and aural fullness, which can fluctuate. Systemic autoimmune diseases coexist in 15-30% of patients.