The degree of hearing impairment of chronic otitis media will indicate the nature and severity of middle ear pathology, especially condition of ossicular chain, size of ear drum perforation and location of granulation tissue in the middle ear cavity. Author studied the relationship between the preoperative hearing acuity and above mentioned middle ear pathology in next four groups. The subjects were 189 ears of tympanoplasty for chronic otitis media and divided into four groups as follows : Normal ossicular chain with only ear drum perforation (group I), normal ossicular chain with granulation tissue only around the ossicle(group II), ossicular ankylosis or fixation of handle of malleus to promontory with or without granulation tissue around the ossicle(group III), and ossicular interruption by partial or complete destruction(group IV). The results were concluded as following : 1) The average hearing threshold of chronic otitis media was 44.6 dB and hearing threshold was closely related to the condition of ossicular chain. Hearing threshold became greater in order of normal ossicular chain, ankylosis and interruption. 2) The average hearing threshold of interrupted ossicular chain group was 49.1 dB and it was greater in the cases of total destruction than that of partial destruction. 3) The hearing loss of the tympanic membrane perforation with normal ossicular chain was within 45 dB and the degree of hearing loss was in proportion to the size of perforation. The hearing loss more than 45 dB was suggested other pathological change in the middle ear cavity. 4) In the type of audiogram, flat and ascending types were most frequently observed, showing 30.2% and 35.4% respectively. Descending type was more frequent in the cases of normal ossicular mobility with granulation tissue around the ossicle and ascending type was observed frequently in the cases of ossicular ankylosis. 5) Prolonged bone conduction threshold on lower frequency was seen in the cases of normal ossicular chain with some loading on the ossicular chain and increased bone conduction threshold on higher frequency supposed to be suggest some damage of the inner ear due to chronic otitis media. 6) Carhart's notch was seen in 14 cases (7.4%), which was observed mainly in ossicular ankylosis. 7) There was no relation between hearing threshold and histopathological type of granulation tissue in chronic otitis media. However the degree of hearing impairment was greatly related to the location of the granulation tissue in the middle ear cavity. So author recognized the granulation tissue compensated the function of interrupted ossicular chian.