Adverse reactions to blood transfusion are not often recognized in the operating room. However, immediate reactions are reported to occur in 5% of patients and delayed reactions in a similar number. Many physicians tend to ignore the risks associated with transfusion and administer blood to achieve some magic end point such as a specific hematocrit or platelet count. Blood products are often administered when crystalloid solutions would suffice. Red cells are administered to increase oxygen carrying capacity and platelets and FFP to promote coagulation. Blood products must not be used as volume expanders. A positive aspect of the AIDS epidemic is increased awareness of disease transmission through transfusion. Many patients are requesting that transfusion be withheld or that they receive only autologous blood. A significant percentage of patients scheduled for elective surgery are candidates for predonation and should be encouraged to do so. Particularly suitable are patients scheduled for spine surgery and total hip replacement.