The audiologic manifestations of otosclerosis are as distinctive as they are varied. When pure stapedial otosclerosis is present, the most prominent audiologic signs are elicited in response to the use of low-frequency stimuli, reflecting the effect that increased stiffness has on the transfer function of the middle ear. Characteristic abnormalities appear on tympanometry, acoustic reflexes, and the pure-tone audiogram. When the disease process extends into the cochlea, a sensorineural hearing loss develops, which may be accompanied by vestibular symptoms and/or tinnitus. Complete audiologic evaluation may prove to be uniquely helpful both in establishing a diagnosis by recognizing the characteristic patterns of stapes fixation and in planning for the surgical, medical, or hearing aid management of the patient with otosclerosis.