55 patients undergoing coronary-artery bypass surgery (CABS) and a comparison group of 20 patients having thoracic or major vascular surgery were investigated preoperatively and 8 days and 8 weeks postoperatively for changes in neuropsychological status, psychiatric state, cerebral blood flow, and neurological signs, this last being assessed also at 24 h. Major persisting neurological changes were rare, but minor abnormalities were significantly more common after CABS than after thoracic or vascular surgery. Neuropsychological deficits were common at 8 days in both CABS and comparison groups, and in about a third of all patients persisted at 8 weeks. Cerebral blood flow was reduced at 8 days in some CABS patients, but this was not significant for the group. Pre-existing cerebrovascular disease was not predictive, but low perfusion pressure and long bypass time were associated with postoperative deficits.