In vivo pathogenicity test of Aeromonas hydrophila were done in this experimental study. The objective of this investigation was to evaluate the virulence properties of Aeromonashydrophilaisolatedfromfrogscollected in swamps.To carry out the experiments 24 frog Hoplobatrachus occipitaliswith an average weight of 49.25± 4.21 g were collected and infected with different concentation of A. hydrophila cells (107, 106 and 105 CFU/ml) and physiological saline (0.85% NaCl)by intramuscularly injection in Laboratory. The observations of different batches of frogs during the 96 hours of experimentation showed that the clinical signs of the disease were the weakening of the animal, the cessation of swimming and the appearance of red spots on the hind legs.Death animals were recordedafter24 hours of injection with a concentration of 107 CFU/ml.The highest mortality rate (33.3%) was obtained 48 hours after injection of the bacteria. In this study, the lethal dose (LD50) of A. hydrophila obtained from the cumulative mortalities was 5.8x106 CFU/ml.