Persistent otorrhea and recurrnet infection are the main causes of revision surgery of chronic otitis media. To fine out causal factors of revision middle ear surgery, 59 cases of revision tympanomastoidectomy and tympanoplasty from Jan. 1985 to Dec. 1992 in Catholic University Medical College Kangnam St. Mary's hospital were investigated retrospectively. The intervals between the 1st operation and the revision operation were from 2 months to 33 years. Mean pure tone threshold was 50 dB in air conduction and mean air-bone gap was 40 dB. Among the 59 cases, tympanoplasty with mastoidectomy were performed in 44 cases(canal down 31 cases, canal up 8 cases, atticotomy 5 cases), and tympanoplasty without mastoidectomy were done in 15 cases. Granulation tissue from unexenterated cells was the most common cause for revision surgery cause for revision surgery(72.9%), especially for tympanomastoidectomy. Perforation of the tympanic graft was the main cause for revision tympanoplasty(61.1%). Residual or recurrent cholesteatoma was another reason for revision tympanomastoidectomies(34.1%).