Abstract: Crucian carps, Carassius auratus, about 70 gram weighs wereexperimentally infected with Aeromonas hydrophila.Various haematological anddisseminated intravascular coagulation(DIC) parameters were compared betweenmoribund and normal fish.The numbers of red and white blood cells, haemoglobin,all decreased in infected fish compared to controls.Erythrocyte sedimentation rateincreased in infected fish.The haematocrit and mean cell haemoglobin concentration for infected fish did not differ significantly from the controls.Diseased fish, incontrast with control fish, showed a marked decrease in the number of leucocytes permilligram of head-kidney.These results suggested that diseased fish were severeanemic.Plasma prothrombin time and thrombin time were significantly longer ininfected fish thou those of control fish.The positive rate of plasma protamine paracoagultion test in infected fish was 80%, while 0% in control fish.Plasmafibrinogen and Plasma coagulation factor X activity decreased in infected fishcompared to controls.It is indicated that infected fish had obvious hemostatic disorderand disseminated intravascular coagulation (DIC) during the infection which accountsfor the hemorrhagic symptom of the diseased fish.