Blood transfusion is expensive, and has medical and safety consequences for patients who benefit from it. In cardiac surgery, the data concerning the level of perioperative transfusion are very heterogeneous from one center to another. In a large US cohort study of 798 cardiac surgery centers and 102,470 patients undergoing coronary artery bypass surgery, the rate of blood transfusion varies from 8 to 93% depending on the center. It would appear that the largest and most experienced centers have a blood transfusion rate of around 60%.