The studies on bacterial distribution in chronic suppurative otitis media were made by many otologists, but there are some difference in them. The bacteriological study was made on 196 cases of the chronic suppurative otitis media who visited the Department of Otolaryngology, Seoul National University Hospital during a period of Aug. 1977 through July 1978 and the following conclusions were obtained. 1) In the 208 of 221 ears in which specimen was collected from the middle ear, 226 strains were isolated and among isolated strains, Proteus was 71 strains (26.7%) in 66 ears, Staphylococcus 55 strains(20.7%), Pseudomonas 49 strains(18.4%) & others 91 strains(34.2%). 2) Simple infection was 154 strains in 154 ears (74.0%) and mixed infection was 112 strains in 54 ears (26.0%). Proteus, Staphylococcus & Pseudomonas were identical in simple infection and Proteus was most prevalent in mixed infection. 3) In the 73 of 102 cases in which specimen was collected from the mastoid cavity, 84 strains were isolated and Proteus was 32 strains(38.1%) in 29 ears, Pseudomonas 14 strains (16.6%), Staphyloccus 11 strains(13.1%). 4) The same pathological organisms cultured from discharge of both the middle ear and the mastoid cavity were found in only about one third. 5) Proteus was 2 times in cholesteatomatous otitis media than non-cholesteatomatous otitis media. 6) No significant difference existed in microorganisms according to seasonal variation. 7) Proteus was highly sensitive to gentamycin (94.7%), Kanamycin(86.8%), carbenicillin(84.8%) and resistant to tetracycline(94.0%). 8) Staphylococcus was highly sensitive to cephalosporin(98.4%), gentamycin(96.1%), methicillin(92.3%) and relatively resistant to tetracycline(80.0%) & penicillin (78.0%). 9) Pseudomonas was relatively sensitive to gentamycin (64.5%).