Cognitive dysfunction is frequently observed after cardiac surgery and presents a major problem for physicians, patients, and their families. Up to this point, no therapy has yet been shown to successfully treat this horrible complication. Recombinant human erythropoietin (rhEPO), a drug used to treat the anemia associated with renal failure or cancer, has tremendous potential to protect the injured brain during vulnerable periods. Although most of this work has been done in animals, one small but exciting study demonstrated that rhEPO was able to improve outcome after stroke. We propose a prospective outcome study in which patients undergoing cardiac surgery will be randomly assigned to receive either intravenous recombinant human erythropoietin (rhEPO) or routine perioperative care (without erythropoietin). Specifically, we will test the hypotheses that perioperative rhEPO administration decreases the incidence of postoperative cognitive dysfunction. Secondary outcomes will also be evaluated, including the incidence of major and minor medical complications. In addition to providing insight into the mechanisms of CPB-induced cognitive dysfunction and the possible responsiveness to rhEPO, this unique study will also allow us to examine the mechanisms of brain aging and dementia as well as propose additional therapeutic modalities.