Sudden hearing loss occurs as the initial symptom in 1 to 9 per cent of all acoustic neuromas. A case of an acoustic neuroma presenting with sudden hearing loss is described. In this case, the hearing thresholds returned to normal. To the authors' knowledge, this is the first case in which an acoustic neuroma presenting with sudden hearing loss exhibited a return to normal thresholds. This suggests that such tumors may have an initial reversible effect on hearing thresholds.