Far-advanced otosclerosis (FAO) is an uncommon diagnosis. Hearing levels in patients with FAO may range from profound loss, by air conduction and fragmentary bone conduction thresholds, to no measurable air or bone conduction thresholds. Thus, FAO may be difficult to distinguish from a sensorineural hearing loss. This report presents the results of surgery in 73 ears with FAO, 77 percent of which had improvement in air conduction thresholds of greater than 20 dB. Discrimination was improved by more than 15 percent in 54 percent of cases, and 75 percent realized improvement in use of a hearing aid. There was no evidence that success was related to preoperative hearing. The surgical results of a subgroup of 14 patients having bilateral FAO were also analyzed. For all 14, similar surgical outcomes were achieved in both the initial and the contralateral ear, with six successes bilaterally and eight failures bilaterally. Although far advanced otosclerosis is uncommon and difficult to diagnose, surgery is worthwhile.