One week after surgery neuropsychological (NP) deficits were quite common, occurring in 40.6% of the patients, with QEEG abnormality developing or increasing in the majority of patients. This change in the QEEG was an accurate predictor of NP performance 1 week after surgery. Two to three months after surgery evidence of continued NP performance deficits were still present in 28.1% of the patients. Preoperative versus one week postoperative QEEG change showed higher levels of sensitivity and specificity for predicting neuropsychological performance 3 months after CPB surgery than did preoperative versus one week postoperative NP performance. The mean values of specificity plus sensitivity were 74.5% for NP performance and 89.1% for the QEEG. These high levels of sensitivity and specificity for QEEG change for predicting postoperative cognitive function may justify the utility of performing these evaluations in the general CPB surgical population. In addition, this evidence supports the need to study the role of intraoperative QEEG monitoring to determine when QEEG change occurs so that possible remediational measures can be taken as soon as possible.