The variability in frequency of allogeneic blood transfusion during coronary artery bypass surgery (CABG) is a concern. Evidence-based guidelines support minimizing the use of blood during open heart surgery. The Hospital Clinical Services Group quality indicator database was queried for intraoperative red blood cell (RBC) transfusions in 17 252 isolated CABG surgery cases during 2007. Institutional variability was observed in the frequency of intraoperative RBC transfusion rates, which ranged from 0% to 85.7%. The institution mean RBC transfusion rate was 40.8%. Regional geographic and cardiac program size variations were observed in RBC transfusion rates and volume with significant variation. Notable institutional variability persists with respect to intraoperative RBC transfusion in isolated CABG surgery despite clear evidence and guidelines to support techniques to minimize RBC transfusion. Such results support the hypothesis that incorporating evidence-based transfusion-related practices in open heart surgery are not uniformly adopted.