Operative techniques of extensive chronic otitis media with or without cholesteatoma could be divided into intact canal wall mastoidectomy and open cavity mastoidectomy. Most of otologic surgeon have accepted the concept fo staging tympanoplasty in intact canal wall mastoidectomy depends on the status of middle ear mucosa, but have controversial opinion in open cavity mastoidectomy. The goal of staging tympanoplasty are to restore healthy middle ear mucosa, aerated middle ear and stable tympanic membrane. We performed clinical evaluation of 50cases of chronic otitis media which were taken staged tympanoplasty with open cavity mastoidectomy and obtained following results. 1) In second stage operation, healthy aerated middle ear were obtained in 92% of cases. 2) Of the forty cases with staged tympanoplasty, Twenty-eight cases(56%) obtained postoperative hearing less than 20dB of air bone gap and fourty-five cases(90%) were less than 30dB of ABG. Comparing this result with twenty-three cases without staged tympanoplasty, the staged tympanoplasty contributed to improvement of post-operative hearing. Also, comparing with twenty-four cases with closed cavity mastoidectomy, the result was almost similar. 3) The twenty-seven cases(54%) obtained post-operative hearing within social serviceable hearing. 4) The eleven cases(22%) lost more than 10dB in bone conduction after operation.