Increased sophistication in blood banking and transfusion practice has opened new directions in management of red cell mass and coagulation. The current trend in practice is to avoid absolute hemoglobin or hematocrit values, and to employ physiologic parameters to determine the need for transfusion. For red cell mass, those parameters include use of oximetry, particularly venous oximetry, calculation of oxygen-carrying capacity using cardiac outputs and arterial oxygen saturation, and the ability of each patient to increase cardiac output and/or maintain suitable arterial pressure with hemodilution. More exacting assessment of the coagulation profile, along with evidence that supports the critical circulating platelet and fibrinogen levels, permits judicious use of blood components.