Neurologic status is of concern in infants with congenital heart defects undergoing open heart surgery. The association between perioperative electroencephalography (EEG) with acute neurologic status and subsequent outcome was examined in a cohort of 60 infants. Preoperative EEG and neurologic examinations were performed within 1 to 2 days prior to surgery (n = 27) and postoperatively (n = 47). Prior to surgery, 15 of 27 infants had normal EEG, whereas 5 had epileptiform activity and 9 had disturbances in background activity that were primarily moderate (8/9) and diffuse (7/9). Postoperatively, only 17 of 47 infants had normal recordings. Newborns (<1 month) were more likely (P< .001) to demonstrate EEG abnormalities than infants. Epileptiform activity was documented in 15, whereas 28 had background abnormalities that were moderate-severe (22/28) and diffuse (20/28) in most. Epileptiform activity prior to surgery was always associated with an abnormal neurologic examination, and this association persisted postoperatively (86%). Moderate to severe background abnormalities in the postoperative EEG was also strongly associated with acute neurologic abnormalities (93%). Severe background abnormalities (n = 5) were 100% predictive of death or severe disability. Long-term follow-up revealed that all children with normal postoperative EEGs had positive neurologic outcomes (P = .04); however, there were many false positives. Perioperative EEG abnormalities increased the likelihood for acute neurologic findings, whereas normal recordings following surgery were reassuring with regard to a favorable outcome.