A case of cortical deafness resulting from CVA due to Moyamoya disease was reported. Patient, a 32 year-old left-handed woman, suddenly became deaf without aphasia. CT scan revealed old infarction in the right fronto-temporo-parietal area and fresh hemorrhage in the left putamen and auditory radiation. Pure tone audiometry showed severe hearing loss of 80 dB in both ears. In Békésy audiometry, excursion of the graph were extremely wide.     During recovery period, we observed that her auditory perception was improved by repetitive auditory stimuli or by stimuli of other sensory modality. Under circumstances where she could predict the occurrence of sound or voice, she was often able to hear them. These phenomena were confirmed by the following experimental results. Audiometry by method of limits revealed that ascending limens were higher than the descending ones by approximately 10 dB in both ears. When flashes were given simultaneously with tone stimuli, thresholds became lower as compared with the condition without flash.     From the clinical observations and experimental results, we presumed that the active process of auditory perception would be disturbed in the mechanism of cortical deafness.