During a 10-year period (1984-1994) 1229 stapes operations for otosclerosis were performed at our respective institutions by experienced surgeons well trained in the various techniques. Procedures included 691 stapedectomies, 234 small-fenestrae stapedotomies, and 304 revision operations. These primary and revision cases resulted in 20 ears with severe sensorineural hearing loss or anacusis noted during the immediate postoperative period. This article will critically evaluate those procedures that resulted in profound hearing loss and attempt to determine possible reasons for this occurrence. It is hoped that these data will allow surgeons to identify before and/or during surgery patients at risk for development of this complication and therefore decrease the overall morbidity rate of this exacting procedure.