Background: The 2007 Society of Thoracic Surgeons and the Society of Cardiovascular Anesthesiologists Clinical Practice Guideline for Perioperative Blood Transfusion and Blood Conservation in Cardiac Surgery was recently promulgated and has received much attention. Using a survey of cardiac anesthesiologists and perfusionists' clinical practice, we aimed to assess the current practices of perfusion, anesthesia, and surgery, as recommended by the Guidelines, and to also determine the role the Guidelines had in changing these practices. Methods: Nontrainee members of the Society of Cardiovascular Anesthesiologists, the American Academy of Cardiovascular Perfusion, the Canadian Society of Clinical Perfusion, and the American Society of ExtraCorporeal Technology were surveyed using a standardized survey instrument that examined clinical practices and responses to the Guidelines. Results: A total of 1402 surveys from 1061 institutions principally in the United States (677 institutions) and Canada (34 institutions) were returned, a 32% response rate. There was wide distribution of the Guidelines with 78% of anesthesiologists and 67% of perfusionists reporting having read all, part, or a summary of the Guidelines. However, only 20% of respondents reported that an institutional discussion had taken place as a result of the Guidelines, and only 14% of respondents reported that an institutional monitoring group had been formed. There was wide variability in current preoperative testing, perfusion, surgical, and pharmacological practices reported by respondents. Twenty-six percent of respondents reported 1 or more practice changes in response to the Guidelines. The changes made were reported to be highly (9%) or somewhat (31%) effective in reducing overall transfusion rates. Only 4 of 38 Guideline recommendations were reported by >5% of respondents to have been changed in response to the Guidelines. Conclusions: Wide variation in clinical practices of cardiac surgery was reported. Little change in clinical practices was attributed to the Society of Thoracic Surgeons/Society of Cardiovascular Anesthesiologists Guidelines.