The results of pure tone audiometry were observed with 241 ears of 168 hard of hearing subjects who came to our department during the period of January to October 1962. Classifications of conductive, mixed and perceptive deafness were made on the basis of otological examination, clinical history, air and bone conduction thresholds. Form of hearing acuity was analyzed by the slope of the air conduction threshold curve. 1) The cases of ear with conductive loss occur most frequently in chronic otitis media, and showing 45% of horizontal form and 44% of ascending form. 2) The etiology observed in the perceptive deafness cases reveals as follows. unknown etiology 23%, presbycusis 21.5%, acoustic trauma 13.1%, streptomycin intoxication 13.1%, infectious disease and others. The audiometry curves of descending, horizontal and abrupt forms are in 71% of the total perceptive deaf cases. 3) Mixed deafness is most commonly seen in the cases of long-standing middle ear disease and shows horizontal form most frequently. 4) Ascending forms are found chiefly in the cases of middle ear disease and shown in head trauma or inner ear diseases in some cases. Descending forms are shown more frequently in inner ear diseases than middle and external ear diseases. Abrupt and Dip forms are presented in drug intoxication, presbycusis, acoustic trauma etc., but horizontal form occurs in every type of deafness. 5) Averages of air conduction threshlds for the speech frequencies are as follows ; In 69 ears (92%) of 75 conductive deaf cases, the pure tone loss are less than 60 db and 64 ears (60%) of 107 perceptive deaf cases fall within 0 to 40 db, while 41 ears (70%) of 59 mixed deafness have hearing loss greater than 41 db.