Background: Group A streptococcus (GAS) is responsible for a wide spectrum of diseases, including mild diseases such as pharyngitis and invasive diseases such as toxic shock syndrome and necrotizing fasciitis. The incidence of GAS infections, including invasive diseases vary over time in relation with variation in the predominant emm types. Recently, the increase of GAS infections in Korea was reported and we experienced an increase in severe GAS infections. Method: GAS isolates previously obtained from clinical isolates at Seoul National University Children’s Hospital (SNUCH) and Seoul National University Bundang Hospital (SNUBH) between 1991 and 2012 were investigated. The clinical characteristics and antimicrobial resistance were retrospectively reviewed. The emm genotypes, pyrogenic exotoxins (SpeA, SpeB, SpeC) and macrolide resistance genes (ermB, mefA) were identified using polymerase chain reaction ( PCR) and sequencing. Results: A total of 158 GAS isolates were investigated. Among these isolates, the clinical diagnosis were as followed; 45 (28.5%) pharyngitis, 39 (24.7%) scarlet fever, 37 (23.4%) skin and soft tissue infections, 21 (13.3%) invasive diseases, 4 (2.5%) PSGN, 2 (1.3%) rheumatic fever, and 10 others. The three most prevalent emm types were emm1 (19.0%), emm12 (18.4%), and emm4 (17.7%). The emm4 type was associated with scarlet fever ( P=0.000) and emm1 type was associated with invasive diseases ( P=0.006), respectively. The resistance rates of erythromycin and clindamycin were 17.2% and 16.0%. Among 25 erythromycin resistant isolates, ermB gene was detected in 8 isolates. SpeB was detected in all isolates and SpeA and SpeC genes were detected in 37.5% and 48.7%. A recent increase in invasive disease was seen; 57.1% (12/21) of all invasive disease were reported in the past 3 years, among those emm1 accounted for 66.7%. Conclusions: The emm1 and emm4 serotype correlated with specific diseases, and the annual trend showed a recent increase in invasive diseases. GAS serotype and disease diversity emphasizes the importance of continuous surveillance on clinical and molecular characteristics of GAS.