Guidelines for transfusion support in patients undergoing coronary artery bypass grafting. Transfusion Practices Committee of the American Association of Blood Banks. We have reviewed the impact of evolving issues in coronary artery bypass grafting (CABG) on transfusion support for these patients. Issues include increased awareness of transfusion risks, reappraisal of traditional indicators triggering transfusion, and evolving alternatives to homologous blood transfusion such as autologous blood and pharmacologic therapy. These issues have been prompted by programs, such as the National Institutes of Health Consensus Conferences, to provide physicians with guidelines for appropriate use of blood components. However, evidence suggests that transfusion practice in coronary artery bypass grafting procedures remains variable and does not take into account the results of recently published clinical studies. We have therefore developed guidelines and recommendations for transfusion support in patients undergoing coronary artery bypass grafting. In summary, they are the following. 1. Institutions with coronary artery bypass grafting programs should establish a multidisciplinary approach to use a combination of interventions designed to minimize homologous blood exposure. 2. Prophylactic transfusion of plasma and platelets are of no benefit and therefore carry an unnecessary risk to the patient. 3. Special request products such as designated blood donation from first-degree relatives should not be used because of the risk of transfusion-associated graft versus host disease. 4. For support of intravascular volume, crystalloids or colloids should be used because they do not have the potential to transmit infection. 