Acoustic tumor surgery provided an ideal model in which to study possible contralateral hearing loss following a destructive surgical procedure on the inner ear. Follow-up audiometric studies were performed on patients with unilateral acoustic tumors who had undergone resection of their tumors. Patients who had obvious causes for contralateral hearing loss, such as chronic otitis media, unrelated otologic surgery, and noise-induced hearing loss, were excluded from this patient population. A total of 380 patients had available pre- and postoperative audiograms. A mean air-conduction threshold (500, 1000, 2000 Hz) of greater than or equal to 20 dB was considered a significant hearing loss. After adjusting these losses for presbycusis, 1.3% of these patients still had a significant contralateral hearing loss. We discuss the possible causes for the development of contralateral hearing loss and examine the possibility that, following surgical manipulation and injury to the inner ear, immunocompetent cells become sensitized to previously unseen inner ear antigens, setting the stage for contralateral inner ear dysfunction. The similarities of this condition to sympathetic ophthalmia are discussed.