The source of the sound came from a loud speaker connected to a beat frequency oscillator. The examinees were all patients with hearing defect or deafness. The localisation of the subjective median for the source of the sound in the horizontal plane of their ears were examined and the results were as follows; 1. The monaural localization was unable to be made. 2. They were able to locate the source between 515 d. b. or more from the threshold (of Intensity) by their poorer ear. 3. In ears with equal hearing, the source of the sound was localized accurately in the median. But when the hearing of one ear was better, the source of the sound localized to that one. 4. The position of his apparent median plane in the horizontal plane was shown as the angular displacement. The longer the period of difficult hearing was, the smaller the angular displacement was. (general type of angular displacement) 5. When the threshold was 50-60 d. b. or more (of sensation level), the angular displacement was very great and did not become smaller as the period difficult hearing grew. 6. In patients with neural deafness the range of subjective median was as small as normal hearing, and in a patient with conductive deafness it was very large. 7. After catheterization in the so-called tubotympanic catarrh the range of subjective median become very small, especially during the early stage. This was due to the improvement of conduction mechanism.