The tonsil is not only important for it's frequent infection, but also foci of a various focal infection such as rheumatism, carditis, glomerulonephritis and so on. And chronic tonsillitis has long been one of the most common disease in the otolaryngologic field, and the tonsillectomy occupies the greater part of operations performed at our department. The bacterial flora of the chronic tonsillitis has been reported by many investigators since the early 20 centry. But the bacterial flora of the tonsil is continuously changed according to the environmental conditions and by use of many chemotherapeutic agents. For this reason, we studied on the recent bacterial flora of chronic tonsillitis, and its susceptibility to various chemotherapeutic agent in 389 cases who received tonsillectomy at the Dept. of E.N.T., Dong Kang Hospital from May 1992 to April 1993. The results were as following : 1) In sex distribution, there were 217 males(55.8%) and 172 females(44.2%). 2) Pathogens were cultured in 382 cases(98.2%), the mixed infection was 288 cases(74%) and the simple infection was 94 cases(24.2%). 3) 663 strains were isolated from 382 cases, which were composed of α-hemolytic streptococcus 334 strains(50.3%), Staphylococcus aureus 59 strains(8.9%), β-hemolytic streptococcus 27 strains(4.1%), Streptococcus pneumoniae 3 strains(0.5%), Pseudomonas aeruginosa 2 strains(0.3%) as pathogenic bacteria, and Neisseria 233 strains(35.1%), Klebsiella 4 strains(0.6%), Enterobacter 1 strain(0.2%) as non-pathogenic bacteria in order. And microfloral distribution rate according to age group was similar to above result. 4) In sensitivity test for Staphylococcus aureus(63 cases), cephalothin, oxacillin, cefazolin, ceftazidime, chloramphenicol, ampicillin/sulbactam, cefoperazon, clindamycin, amikacin were noted to be susceptible, but ampicillin, tetracyclin were noted to be resistant. For α-hemolytic streptococcus(56 cases), ceftazidime, cefoperazon, amikacin, cephalothin, ampicillin/sulbactam, cefazolin were noted to be susceptible, but ampicillin, Tetracyclin were noted to be resistant. For Pseudomonas aeruginosa(2 cases), amikacin, carbenicillin, colistin, gentamicin, tobramycin, ceftazidime, cefoperazon were noted to be susceptible, but ampicillin, cephalothin, chloramphenicol, kanamycin, tetracycline, ampicillin/sulbactam, cefazolin were noted to be resistant.