Group A hemolytic streptococci is one of the frequent causes for throat aliments. We sometimes observe various symptoms in the patients infected with group A hemolytic streptococci. Such a patient may suffer severe sore throat, high fever, and various other serious symptoms from the focal infection. In this study, an experiment was concluded to determine antibiotic susceptibility of group A hemolytic streptococci in the throat culture. The effect of the time factor on the maintenance of the susceptibility was also considered. In this experiment 2,120 normal elementary school children were observed. Out of 2,120 throat swabs sampled 80 strains indicated group A hemolytic streptococci. Of these 80 strains, 56 strains were those of males, and 24 of females. The following antibiotics have been used for the experiment. 1) Ampicillin 2) Carbenicillin 3) Cephalothin 4) Colistin 5) Erythromycin 6) Gentamicin 7) Kanamycin 8) Penicillin 9) Streptomycin 10) Tetracycline 11) Vancomycin. The result of the experiment may be briefly summarized as follows : 1) Determination of susceptibility by disc method ; a) Erythromycin, Tetracycline and Carbenicillin showed substantial susceptibility in 77 strains(96.25%). b) Amplicillin and penicillin showed susceptibility in 74 strains(92.50%). c) Colistin showed no susceptibility. 2) Determination of susceptibility by agar plage dilution method : Ampicillin displayed inhibition of bacterial growth to the maximum extent of 100% in the concentration of 100mcg per 1ml, Carbenicillin in the concentration of 200mcg, and Erythromycin, Penicillin and Tetracycline in the concentration of 50mcg respectively. Considering the changes of susceptibility of antibiotics over time, an experiment of this kind should be conducted on an annual basis.