This study represents a prospective, randomized assessment of the potential clinical and economic benefit to be derived from the continuous non-invasive monitoring of regional cerebral oxygen saturation (rSO2) during cardiac surgery employing cardiopulmonary bypass (CPB). Previous studies have shown that low rSO2 values obtained during surgery are highly associated with postoperative frontal lobe dysfunction, cognitive declines, disorientation, and other clinical indices of prolonged recovery. Low rSO2 values are thought to reflect the development of tissue hypoxia within susceptible regions of the cerebral cortex during the non-pulsatile perfusion of CPB. Rapid detection and correction of such episodes should help avoid regional hypoxia and its attendant postoperative sequelae. This study will assess neurologic, psychometric, and quality of life markers of brain dysfunction which could result from CPB. Each study patient will be assessed both pre- and postoperatively (pre-hospital discharge and at three months) for neurologic and neurocognitive dysfunction.