Chronic suppurative otitis media is a diagnosis of chronology and history that sustains repeated or persistent infection manifested by mucopurulent discharge, and is one of the most common disease in the otolaryngologic field. There are many reports in this study but there are some differences each other. The author has performed the bacteriologic study in 115 cases(male 70, female 45) of Chronic suppurative otitis media who visited the department of otolaryngology, Chung-Ang University Hospital during a period of January 1983 through December 1984 and following results were obained. : 1) In age distribution, 3rd decade was most prevalent(31.3%) and next were 4th decade(25.2%). 2) 0-4 years was most common duration(23.0%) and next was 20-24 years(20.0%). 3) Among 115 cases, 92 cases(80.0%) were unilateral, in details, right ears were 47 cases and left ears were 45 cases and 23 cases were bilateral(20.0%). 4) The positive cultures were 110 cases(95.7%) but 5 cases were no growth. Among 100 cases, single infection was 93 cases(84.5%) and mixed infection was 17 cases(15.5%). 5) The most freguently isolated bacterium was Pseudomonas aeruginosa(34 strains, 26.8%) and next were Staphylococcus aureus(32 strains, 25.2%) and Staphylococcus epidermidis(15 strains, 11.8%) and Proteus mirabilis(10 strains, 7.9%). 6) Pseudomonas aeruginosa was sensitive to Cefobid(93.7%), Tobramycin(93.1%), Amikin(87.9%), and resistant to Tetracycline(83.3%), Cefotaxime(46.7%). 7) Staphylococcus aureus was sensitive to Cefobid(100%), Cephalothin(100%), Penicillin(96.8%), Tetracycline(77.3%), chloramphenicol(40.6%). 8) Staphylococcus epidermidis was sensitive to Cefobid(100%), Cefotaxime(100%), Cephalothin(100%), Cefamandole(100%) and resistant to Tetracycline(86.7%), Penicillin(85.7%), Chloramphenicol(56.2%). 9) Proteus mirabilis was sensitive to Cefobid(100%), Cefotaxime(100%), Amikin(100%), Gentamicin(100%) and resistant to Tetracycline(77.8%), Chloramphenicol(50.0%), Kanamycin(40.0%).