Chronic otitis media is one of the frequent diseases in otolaryngologic field. Many authors made study of chronic otitis media bacteriologically, and there has been increasing trends of resistant strains to antibiotics because of inadequate use of antibiotics for chronic otitis media. We performed the bacteriological survey of 151 patient which visited in the department of otolaryngology, National Medical Center during the period of 6 months from April to September, 1976 and also analyzed 201 strains and its sensitivity test to various antibiotics. The following result were obtained : 1. Among the various pathogenic bacteriae detected from middle ear (201 strains), staphylococcus group was 37.81% and the others were proteus group 21.89%, pseudomonas group 7.96%, diphtheroid group 5.97%, streptococcus group 4.47% in order of frequency. 2. Among the all cases (151 patients, 201 strains), 129 cases were affected unilaterally and 22 cases were affected bilaterally. 3. About the sensitivity to antibiotics, methicillin (100%), leucomycin (98.41%), cephalosporin (69.44%), cloxacilline (68.62%), gentamycin (65.39%) were highly sensitive but furadantin (100%), colistin (77.59%), sulfadiazine (73.81%), chloramphenicol (70.83%), doxycycline (69.91%), tetracycline (68.35%), penicillin (60.53%) were highly resistant. 4. About the mixed infection, staphylococcus aureus with proteus mirabilis was 11 cases (22%) and the others were proteus mirabilis with diphtheroid-6 cases (12%), proteus mirabilis with enterococcus-6 cases (12%), staphylococcus aureus with pseudomonas aerugionsa-4 cases (8%) in order. 5. Staphylococcus group were sensitive to methicilline (100%), gentamycin (100%), leucomycin (98.11%), cephalosporin (83.78%) and resistant to furadantin (100%), tetracycline (70.67%), penicillin (69.88%). Proteus group were sensitive to carbenicilline (80.85%), cephalosporin (79.79%) and resistant to colistin (100%), furadantin (100%), tetracycline (93.75%), erythromycin (93.84%), doxycycline (92.0%). Pseudomonas group were relatively sensitive to gentamycin (75.86%) and resistant to streptomycin (100%), tetracycline (100%), colistin (100%), carbenicilline (85.0%). Diphtheroid group were sensitive to methicilline (100%), leucomycin (100%), cloxacillin (100%), erythromycin (85.71%) and resistant to penicillin (80%), tetracycline (75.0%), ampicillin (100%), doxycycline (100%).