Group A Streptococcus strain ST4529 is a provisional new ems type which has been recently reported in Malaysia (Jomal, et al. 1999. Energ. Infect . Dis. 5,10-14). This strain was found to be opacity factor (OF) negative with a Tl phenotype. Usually, OF negative strains with T1 phenotypes are associated with acute rheumatic fever. However, strain ST4529 was isolated from the blood of a patient with septicemia. Comparison of the deduced amino acid sequence of the mature hypervariable N-terminus of ST4529 showed only 43% identity with that of M5, the closest matched OF negative strain with a T1 phenotype. Thus, ST4529 most probably encodes a new serospecifically unique M protein which is associated with septicemia rather than pharyngitis infections. The strains with these phenotypes are very important because their sequences should be considered for developing any anti-streptococcal vaccines.