In an attempt to locate lesions in the auditory system, the author examined 46 cases of perceptive low tone deafness by various methods of hearing were bilaterally.involved and five unilaterally. Hearing was estimated by performing the tment test, temporaly threshold shift test using a Bekesy type audiometer, distorted speech perception test with use of 1200 cps low pass and 1700 cps high pass filters, and binaural hearing test using an interchannel time difference (ITD) apparatus. The vestibular function was also examined by observing spontaneous, positional and positioning netic pattern tests. Differentiation between the peripheral and the retrolabyrinthine lesions was anticipated from the results.It was concluded that the lesion in the patient of perceptive low tone deafness was peripheral, retrolabyrinthine or both, suggesting a systemic disease in the auditory system.