By conducting hearing tests on 618 pupils of the third year in the elementary school in a sound proof room with the use of an 8-pure tone audiometer along with observations of adenoid hypertrophy by aid of nasopharyngoscope the author carried out detailed examinations of the nose, ear and throat. As for the criterion of deafness, ones that can not hear 2 tones at 20 db or one at 25 db were considered deaf. Deaf ears and doubtful cases for deaf determined by the method just mentioned, were re-examined on two other occasions and the changes in their hearing were investigated. Regarding subjective symptoms as to the hardness of hearing, careful attention were paid on the records previously prepared at individual's home and as the results the following data obtained. 1. The number of those who had been considered to be deaf at the first test gradually decreased significantly at each of of two subsequent tests. 2. The percentage of deaf pupils proved to be 14.8 per cent, while that of deaf ears 11.9 per cent of the total examined. 3. The majority of those who had been considered deaf on the first hearing test but adjudged to be of normal hearing on the following tests, showed the fall in the threshold at 8124 cps.. 4. Therefore, in order to determine the hardness of hearing in young persons it is necessary to pay a special attention to a higher tone and to conduct hearing tests at least three times on different days. 5. Those who were unconsciously deaf amounted to 67.0 per cent of the total deaf pupils, and the same among those whose deafness proved to be slight, namely, witihn average 25 db at speech range in both ears, amounted to 80.8 per cent. 6. Most of unconscious deafness had their origin in the Eustachian tube: and cases with unconscious deafness in both ears having the origin at the tube amounted to 90.2 per cent and the same in one ear amounted to 75.0 per cent. 7. Deafness with its origin at the Eustachian tube occupied the major portion (86.8% ) of those slightly hard of hearing within average 25 db at speeeh range. 8. The lesions of the nasal cavity and the pharynx that had been associated with deafness were simple chronic rhinitis, hypertrophic rhinitis, sinusitis and deviation of the nasal septum. Comparing the incidence of deafness in the ears with these lesions to those without lesions, deafness proved to be more predominant in the ears with the lesions. 9. Deafness in both ears were found quite many among the pupils of poor scholastic standing.