Identification of group A $eta$-phemolytic streptococci is very important to provide an appropriate preventive measure of possible rheumatic fever and acute glomerulonephritis. For such purpose bacitracin susceptibility of streptococci because of its simplity has been most widely used despite of its occasional faulty results. Recently, a coagglutination technique was advocated using streptococcal group specific antibodies adsorbed to protein A-containing staphylococci. This study was conducted to evaluate the coagglutination technique using reagents prepared by ourselves. The specificity, reproducibility and stability were ascertained and the following results were obtained. 1. The identification by coagglutination technique using our own reagent gave the same results compared with the Lancefield precipitation technique. The result also agreed with the Phadebact grouping. 2. There were no variation in group A and B identification due to lot difference. However, there were a few discrepant results in group C and G identification which was conducted in different days with different lots of our reagent. 3. The stability of our reagents was less satisfactory compared to the commercial product. An effort to improve the stability was considered necessary. 4. For coagglutination, it was found convenient to use supernatant of Todd-Hewitt broth incubated for 24 hours. Both parafin-ringed slide glass and RPR card gave comparable results and the former could be used when the latter is not available.