The operative findings of 97 revision tympanomastoid surgery among 1992 cases of chronic otitis media were retrospectively analyzed to clarify the causes of failure after middle ear surgery. The patient's mean age at revision surgery was 29 years old and the mean interval between the primary and revision surgery was 5.2 years. The mean age at primary surgery was 23 years old and 22% of the patients were operated under the age of 15. Most of the patients were operated two times(95%), however, three patients were operated three times and one patient was operated up to five times. In primary surgery, the cholesteatoma was comprised 48%. The operative procedures were the intact canal wall in 34% and open cavity mastoidectomy in 40%, respectively. In the revision surgery, the cholesteatoma was comprised 40% and 55% of the cholesteatoma patients were operated by the open cavity mastoidectomy. Among the 35% primary intact canal wall patients, 10% of patients were changed to the open cavity mastoidectomy in the revision surgery. The main presenting symptoms for the revision surgery were the otorrhea in 73 cases(75%), hearing loss in 17(18%), and vetigo in 3(3%). The most common cause of the revision surgery was the cholesteatoma. Among the 40 cholesteatoma in the revision surgery, 24 patients(60%) were the recurrent or residual cholesteatoma 12 patients who did not have cholesteatoma in primary surgery showed cholesteatoma in revision surgery; the causes of the cholesteatoma were the atticotomy in three, perforation of the posterior canal wall in two, and invaginated Palva flap in one. The causes of the remaining 7 patients could not be clarified. The common problems in the open cavity mastoidectomy were the high facial ridge in 40% and stenotic ear canal in 23%. In the 9 cholesteatoma patients who were operated by atticotomy, atticoantrostomy, or transcanal tympanoplasty were all encounteded recurrance of the cholesteatoma in the revision surgery.