Hearing loss in chronic otitis media, closely related to the middle ear pathology, especially, size of ear drum perforation, condition of ossicular chain, location of granulation tissue, and duration of the disease. Author studied the relationship between the preoperative hearing acuity and middle ear pathology in 400 ears of chronic otitis media who had tympanoplasty at Dept. of Otolaryngology in Korea University, Guro Hospital from September 1985 to August 1987. The results were as follows. 1) Hearing loss was increased with the increase in duration of the disease, but the cholesteatoma was not increased. 2) Hearing loss was increased with the size of ear drum perforation and cholesteatoma was the most common in attic perforation 3) Hearing loss increased in order of simple perforation without pathology, ossicular fixation, pathologic lesion around the ossicles, ossicular disruption, total loss of ossicles. 4) Hearing loss more greatly related to the middle ear pathology than the size of drum perforation. 5) Hearing loss was greater in two or more loss of ossicles than single loss and average 67.8% cases of ossicular losses were related to the cholesteatoma. 6) In the type of audiogram, flat type was the most common and ascending type was next common.