Background and Purpose-As a result of advances in surgical, anesthetic, and medical management, cardiac surgery can now be performed on older, sicker patients, some of whom have had prior cardiac interventions. As surgical mortality has declined in recent years, attention has focused on the complications of stroke and encephalopathy after cardiac surgery. Summary of Review-Patients with preexisting cerebrovascular disease are at increased risk for these untoward neurological outcomes, which are associated with longer lengths of hospital stay, higher costs, and greater mortality. The mechanisms underlying these neurological events may include microemboli and hypoperfusion during surgery, and postoperative atrial fibrillation. Predictive models, based on information available before surgery, allow identification of these "high risk" patients. Conclusion-Establishing the degree of functionally significant vascular disease of the brain before surgery should be an essential part of the preoperative evaluation, particularly when modifications in surgical technique or novel neuroprotective agents are being evaluated. (Stroke. 2006;37:562-571.)