The role of transfusion in surgery and trauma continues to evolve with our greater understanding of the true indications for and effects of transfusion. The potential adverse immune consequences and end-organ effects of blood transfusion must be weighed against the need for replacement of blood volume and oxygen-carrying capacity. The techniques to conserve blood and avoid transfusion play an important role in caring for the bleeding surgical patient. The future holds great promise for the possibility of redefining the art of blood transfusion and perhaps one day replacing it entirely.