Past research has indicated that binaural hearing abilities are not always normal in patients having otosclerosis who have received bilaterally normal pure-tone thresholds through stapedectomy. This study investigated whether poststapedectomy performance on the binaural masking-level difference test could be predicted from presurgery tests in which the two ears were stimulated at an equal sound pressure level and at an equal sensation level. Results indicated that (1) binaural hearing usually improved following stapedectomy, though some patients maintained abnormally poor binaural hearing even though postsurgery pure-tone thresholds were normal; and (2) prediction of postsurgery results was poor, with postsurgery results often being underestimated from presurgery results. Results are interpreted in terms of possible forms of auditory deprivation and acoustic crossover.