The bleeding method is the most widely used technique in volume controlled hemorrhagic shock model that was described as withdrawing blood by an heparinized syringe from veins of laboratory animals. However the difficulty in establishing a constant bleeding rate and volume at a desired time is the major disadvantage of this technique. This disadvantage may also lead to the mortality during the exsanguinating phase due to inconstant bleeding rate. Reversely connected infusion pump that was described in this report is a useful and practical method to withdraw blood with predetermined bleeding volume and rate. The described method can easily be applied to various pathophysiological and metabolic studies on acute blood loss.