The aim of this study was to identify the microorganism in the discharge from 58 operated middle ears and to assess the drug sensitivity, 11 different chemotherapeutic agents. The following conclusions were obtained ; 1) The bacterial species were isolated as follows ; staphylococci (25), E. coli (14), proteus species (9), streptococci (3), Pseudomonas (3) and Gram (+), bacilli (3). 2) Mixed infection was observed in 7 cases, most frequent species were staphylococci and E. coli. 3) In sensitivity tests, gentamicin, nalidixic acid and bactrim were effective in the most of strains. Gentamicin and nalidixic acid were very sensitive to E. coli, pseudomonas and proteus species.