About the microorganism of chronic otitis media, several reports were found but differ from each other about the distribution of microorganism and it's sensitivity to antibiotics. Author reviewed 100 patients of chronic otitis media from May 1 '74 to Aug 31 '74 in National Medical Center and analyzed 137 isolated strains and its sensitivity to antibiotics. Following results were obtained ; 1) male patients (63%) were more than females (37%). 2) 11-20 year olds were most prevalent (49%). 3) About duration time, 41% of patients were 1-5 year-olds. 4) Among isolated strains (137), staphylococcus were 55 strains (40.2%), proteus 32 strains (233.5%), streptococcus and pseudomonas 14 strains (10.22%) respectively. 5) The percentage of sensitive strains were higher against leucomycin 100% methicilline 96.7%, gentamicin 85.5%, cephalosporin 75.4% and cloxacilline 70%. The percentage of resistant strains were higher againist penicilline 91.7%, colistin 90.3% and teramycin 86.5%. 6) Staphylococcus strains were sensitive to methicilline (100%), gentamicin (100%), cephalosporin (100%), leucomycin (100%), and streptomycin (83%), and sesistant to penicilline (89%), and teramycin (86%). Pseudomonas was highly resistant to colistin (100%), cephalosporin (100%), and teramycin (100%), and relatively sensitive to gentamicin (70%). Proteus was sensitive to carbenicilline (88%), gentamicin (87%), cephalosporin (81%) and streptomycin (75%), and resistant to panicilline (100%), erythromycin (100%), colistin (100%) and doxycyline (92%).