Accurate knowledge of the total blood loss during surgery, helps to get maximum benefit from transfusions. Blood should be given to the volume and rate of loss. The maintenance of circulating volume of red blood cells in the normal range, should consider it as an elementary fact in surgery patients with poor surgical risk, particularly in heart, arteriosclerotic and those elderly who can not tolerate either an overload or a decrease in circulating volume. The methods used to measure blood loss during surgery are discussed. The authors apply the gravimetric method and recommend it as a routine procedure during surgery. A personal estimates of total blood lost during surgery is worthless. When it comes to control massive bleeding from several liters, the error can be so large that a lack of action may endanger the patient's life. The total blood loss during the operation obtained by the me...