AbstractThis paper reported sixteen bacterial strains isolated from fishes naturally infected by epidemic septicemia (including silver carp , bighead carp and common carp) . Of them , eight evidently caused disease , especially SC96-1-1 and SC96-2-4 caused deadly disease and the incidence is up to 100 % during 4～24 hours. All isolates were determined in growth , physiological characteristics and classification. The results showed that they shared following characteristics : gram-negative rod , motile , oxidase positive , V-P positive , glucose and mannitol fermentative , but not inositol fermentative , not urea decomposite. These features indicated that the pathogen of epidemic septicemia occurred in Beijing belonged to Aeromonas hydrophila. This result provides scientific basis for the prevention and cure of this infectious disease.