Abstract: A total of 28 Aeromonas strains obtained from water and diseased fish in South Korea were examined for virulence gene screening. Strains were tested by multiplex PCR for the presence of 2 β-hemolysins genes and 3 Type III Secretion System (TTSS) genes. All A. hydrophila strains carried both aerA genes and ahh1 genes and 5 out of the 8 A. sobria strains carried asa1 genes for β-hemolysins. Additionally, 11 strains carried aopB, aopD or ascV genes for TTSS (aopB gene was detected in 7 A. hydrophila strains and 4 A. sobria strains, aopD gene was detected in 5 A. hydrophila strains and 1 A. sobria strains and ascV gene was detected in 4 A. hydrophila strains and 3 A. sobria strains). Interestingly, some sequence of TTSS genes from tested A. hydrophila showed strong genetic variation to those of the reported A. hydrophila, the aopB genes of strain (SNUFPC-A3) was 94% homologous to A. salmonicida (Accession No. AJ616218.2) those of strains (SNUFPC-A10 and CASAH2) were 98% homologous to A. sobria (Accession No. EF215451.1) and the aopD genes of strain (CASAH2) was 98 homologous to A. sobria (Accession No. EF215451.1).