Hemodynamic values were assessed in cows with naturally mastatis. hemodynamic tests included WBC, RBC, PCV, Hemoglobin, Monocyte, Eosinophil, Neutrophil, Lymphocyte, and prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, platelet, antithrombin-III, and plasminogen activities. Significant changes were observed in the mean values of most analytses : WBC, monocytes, eosinophil, neutrophil were increased and Iymphocyte were decreased. prothrombin time was increased： activated partial thromboplastin time, thrombin time. increased : activated partial thromboplastin time, thrombin time, fibrinogen concentration, plasminogen activity and platelet concentration were decreased : and RBC, PCV, hemoglobin and antithrombin-III activity were unchanged, compared with normal mean values. Thesse data indicated activation of hemodynamic mechanisms, initiated either directly by bacteria produced endotoxin of secondaly inflammatory mediators produced in response to caused bacteria and naturally acquired mastitis was very similar to the experimental endotoxin-induced mastitis.