The etiology and pathophysiology of chronic otitis media with cholesteatoma are not clearly understood, but it is known that the disease can be treated by means of complete removal of cholesteatoma and involved lesions. The difficulty of this surgical method, however, lies in improving hearing with preservation of normal structure of the ear as much as possible. To solve this difficulty, several studies have been done and new technics have been developed. However, because of different opinions on the operation technics among the researchers and high incidance of post operative recurrence, there still remain several problems. Clinical analysis, especially on the post-operative complication and post-operative improvement of hearing, has been made according to the extension of disease and to the methods of operation. The materials were composed of 342 ears which had chronic otitis media with cholesteatoma and were operated at Department of Otolaryngology, Yonsei university College of Medicine from Jan, 1975 through Dec, 1981. The results obtained were as follows : 1) There are 28 cases of children under 15 years old and 314 cases of adults over 16 years old. Out of these cases, 22 cases (77.8%) of children had cholesteatoma extended to mastoid process and 189 cases (60.2%) in adults. 2) As a condition of ear drum, 171 cases (50.0%) had total perforation, 95 cases (27.8%) had attic perforation and 50 cases (14.6%) showed central perforation. 3) As a complication, 5 cases (1.5%) had facial paralysis, 5 cases (1.5%) had retroauricular fistula, 2 cases (0.6%) had labyrinthine fistula and 2 cases (0.6%) had menigitis. 4) Pre-operative hearing with pure tone audiogram were. 217 cases (63.5%) had conductive hearing loss, 93 cases (27.1%) had mixed hearing loss and 24 cases (7.0%) had deafness. 5) Post-operative failure rate at 3 months were, 44 cases (12.9%) had draining ear and 33 cases (12.4%) had drum uptake failure. Main result of failure was draining ear (23.8%) among open technic group and drum uptake failure (16.9%) among closed technique group. 6) As post-operative complication, wound infection was found in 23 cases (6.7%), mainly among closed technique group with 15 cases (12.1%), 4 cases (1.2%) had post-operative deaf. 7) Out of 57 cases, that underwent post-operative audiogram, 26 cases (45.6%) were found to have hearing improvement. There was no difference of hearing improvement between open technic and closed technic. 8) As causes of revision, out of 67 cases, that underwent revision, 26 cases were planned second staged operation, 19 cases had residual cholesteatoma and 8 cases had recurrent cholesteatoma. 9) Out of 124 cases, that underwent closed cavity mastoidectomy with tympanoplasty, 99 cases (79.8%) were planned for staging the operation and among them, only 29 cases (29.3%) had second staged operation. The mean duration between first and second operation was 9.8 months. 10) In staged operation, the condition of ossicle and hearing impairment are related in such a way that it is considerably improved in presence of malleus handle and arch of stapes. From this study, I was able to find out that hearing improvement is influenced by the presence of malleus handle.