The article discusses landmark studies that have changed the practice of transfusion medicine. Evidence-based medicine requires the careful application of formal rules of evidence to evaluate the available data in the medical and/or scientific literature. The effective implementation of evidence-based medicine requires that the clinical management of each patient and the establishment of policy be based on the best evidence available at a given point in time. Over the period of time, fewer than 100 randomized controlled trials (RCTs) have been performed to evaluate the various transfusion medicine interventions recommended for use in the treatment of patients. The focus of the transfusion medicine related RCTs has ranged widely and has covered the gamut of transfusion medicine issues.