The aim of this study was to detennine whether Aeromonas hydrophila is a hemorrhagic pathogen in snakehead fingerlings. Clinical signs of floating and impaired swimming, hemorrhagic and ulcerative lesions on the fish body, and protruding scales were observed among cultured snakehead (Channa striata) fingerlings in Co Do, Can Tho city. A strain of A hydrophila, designated CD1012, was isolated from these animals. The pathogenicity of this isolate was assessed at the College of Aquaculture and Fisheries, Can Tho University, using intraperitoneal injection in snakehead fingerlings with bacterial concentrations (as used for the challenge test) of 3.67x10 exponent 3, 3.67x10 exponent 4, 3.67x10 exponent 5 and 3.67x10 exponent6 CFU/fish. Inoculation with A hydrophila CD1012 was associated with clinical signs similar to those seen in naturally infected fish. Resulting mortality indicated that the cumulative mortality of snakehead fingerlings challenged with A hydrophila was tracked for the 14 days post-inoculation test. Mortality was bacterial-dose dependent, with 100 = 0.0 percent mortality observed at 13 days at the highest dose level (3.67x10 exponent 6 CFU/fish). For comparison, noninjected and saline-injected fish exhibited cumulative mortalities of 0=0.0 percent and 6.67=0.0 percent, respectively. The median lethal dose (LD50 was 1.16 x10 exponent 5 CFU /fish. A total of 12 bacterial strains of Aeromonas were reisolated from artificially challenged fish and re-identificated based on morphological characteristics and biochemical tests. No bacteria were isolated from the both groups of non injected and saline injected fish. Two of the re-isolated bacterial strains (CT1107 and CT1109) were characterized by molecular methods. The results revealed the presence of a 209-bp amplicon diagnostic of A hydrophila. The present study results defined that Aeromonas hydrophila is a pathogen infecting to snakehead fingerlings in challenged condition.