A clinical and bacteriological observation was performed in 128 cases of chronic otitis media who undergone middle ear surgery at the department of otolaryngology of St. Benedict Hospital during the period from January, 1983 to December, 1984. The following results were obtained : 1) Among the total of 128 cases, 60 cases(46.9%) were male and 68 cases(53.1%) were female. The age distribution showes 48 cases(37.5%) in third decade, 37 cases(28.9%) in second decade, and 27 cases(21.1%) in 4th decade. 2) The sites distribution revealed in 71 cases(55.5%) in the right ear and 57 cases(44.5%) in the left ear. 3) Central perforation was observed in 65 cases(50.8%), total perforation in 44 cases(34.4%), attic perforation in 12 cases(9.4%) and marginal perforation in 7 cases(5.4%). 4) Degree of pre-operative hearing loss was moderate in 74 cases(57.8%), mild in 25 cases(19.5%), severe in 24 cases(18.7%) and 5 cases were normal. 5) The routes of surgical approach were post-auricular in 123 cases(96.1%), preauricular in 3 cases(2.3%) and transmeatal in 2 cases(1.6%). 6) The types of anesthesia were local anesthesia in 101 cases(78.9%) and general anesthesia in 27 cases(21.1%). 7) The pathological changes of middle ear showed granulation in 82 cases(64.1%) and cholesteatoma in 46 cases(35.9%). 8) The extent of cholesteatoma was attic-antrum in 16 cases(34.8%) attic in 13 cases(28.2%), attic-antrum-middle ear in 12 cases(26.1%), antrum in 3 cases(6.5%), attic-middle ear in 1 case(2.2%), and middle ear in 1 case(2.2%). 9) The types of mastoid surgery were so-called closed cavity mastoid surgery in 95 cases(74.2%), and open cavity mastoid surgery in 33 cases(25.8%). 10) The types of middle ear surgery were intact canal wall mastoidectomy with tympanoplasty in 67 cases(52.3%), atticotomy with tympanoplasty in 28 cases(21.9%), modified radical mastoidectomy with tympanoplasty in 18 cases(14.1%) and radical mastoidectomy in 15 cases(11.7%). 11) Type I tympanoplasty was performed in 15 cases(11.7%), type II in 32 cases(25%), Type III in 36 cases(28.2%), type IV in 5 cases(3.9%), Stage operation in 25 cases(19.5%) and revision in 10 cases(7.8%). 12) The status of ossicles revealed as destroyed in 79 cases(61.7%) and as intact in 49 cases. Destruction of malleus and incus was in 29 cases(22.6%), total destruction was in 24 cases(18.8%), incus destruction only was in 20 cases(15.6%), malleus destruction only was in 4 cases(3.1%), and stapes and incus destruction in 2 cases(1.6%). 13) The graft materials for columella were incus in 24 cases(58.5%), malleus in 15 cases(36.6%), tragal cartilage in 1 case(2.4%), and mastoid cortical bone in 1 case(2.4%). 14) Among 95 culture specimens, proteus was 30.5%, staphylococcus 29.5% pseudomonas 23.1%, Streptococcus 8.4% and others 8.5% in the order of frequency.