Four groups of experiments were focused on two problems: first, the replacement of the substracted amount of blood, and second, the correction of the peripheral reactions to substantial blood loss, namely vasoconstriction and acidosis. We stuck to a simple plan in our experiments: lost blood was entirely collected and retransfused. In 26 cases out of 37, we used isoproterenol hydrochloride (Isuprel®-WINTHROP) to open the peripheral vascular bed. In six different groups, we followed the response to variations of retransfusion and administration of isoproterenol. Several parameters were studied: arterial blood pressure, central venous pressure, rectal temperature and pH. The association of blood transfusion with injection of isoproterenol, in adequate amounts to correct hypovolemia and to prevent vasoconstriction, is undoubtedly the best treatment of hemorrhagic shock.