Serological methods for the epidemiological study of Streptococcus pyogenes, such as T-, or M-typing, were replaced by emm typing in the 2000s. The frequency of emm types may differ according to geographical area and study period. Erythromycin resistance rates and the prevalence of erythromycin-resistant phenotypes in several countries are surveyed, and common emm genotypes associated with erythromycin resistance are described for each country. There is no correlation between erythromycin resistance and macrolide use in Korea. S. pyogenes is thought to cause severe illness, such as streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis. The mortality rate of STSS is about 50%, and there have been several hundred victims of STSS in Japan in the last 2 decades. The resistance rate to macrolides peaked at 50% in 2002, and currently, ＜10% of strains exhibit macrolide resistance in Korea. However, the erythromycin resistance rate recently exceeded 90% in China. Considering increases of travel between neighboring countries, a vigilant survey to monitor these highly virulent and antibiotic-resistant strains is necessary. (Korean J Clin Microbiol 2011;14:119-125)