We assessed the change in intraoperative cerebral oxygen metabolism during coronary artery bypass grafting (CABG) in patients with cerebrovascular desease (CVD) identified by preoperative computed tomography or magnetic resonance imaging. The study population consisted of 36 patients who underwent consecutive CABG and were divided into two groups on the basis of preoperative CVD. With near-infrared spectroscopy, the change in oxygenated hemoglobin/total hemoglobin ratio (%Oxy-Hb), which was regarded as regional tissue oxygenation, was obtained. In addition, jugular venous bulb oxygen saturation (SjO₂) was measured simultaneously. Moreover, the influence of intraoperative parameters on cerebral oxygenation was assessed by regression analysis. Thirteen patients (36%) were given a diagnosis of CVD preoperatively (group A) and were compared with the remaining 23 patients as controls (group B). All of group A were asymptomatic cerebral infarction. The average %Oxy-Hb was 51.2±4.1% in group A and 62.0±12.1% in group B (p=0.04), and SjO₂ was 63.5±8.6%in group A and 68.1±7.7% in group B (p=0.12). In serial changes, %Oxy-Hb during the late phase of cardiopulmonary bypass (CPB) and SjO₂ during the early phase of CPB were significantly lower in group A. The positive correlation between perfusion pressure and SjO₂ was demonstrated in groupA (r=0.699, p<0.0001) while no correlation was observed in group B. It is concluded that patiens with silent cerebral infarctions had poorer intraoperative cerebral oxygen metabolism during CABG. It is necessary to keep a higher perfusion pressure in these patients during CPB because cerebral autoregulation may be impaired.