A case of hyperacusis after tympanoplasty is presented. A 62-year-old woman experienced unilateral conductive hearing loss for about 60 years after antrotomy in infancy. Neurological or otoneurological symptoms were not evident. Tympanotomy showed a missing incus with discontinuity of the chain. Reconstruction was performed by interposition of a partial ossicular replacement prosthesis (PORP). The postoperative audiogram revealed minimal perceptive hearing loss in the high-frequency field in the operated ear. Several weeks after middle ear surgery, the patient complained of hyperacusis on the operated side, which persisted for more than 2 years. To alleviate the unpleasant sensations, an ear plug was used by the patient. In spite of the asymmetric hearing loss, no late onset auditory deprivation could be diagnosed. The pathophysiological causes of the hyperacusis have not yet been clarified. Possible reasons are discussed.