Leukoaraiosis (chronic ischemic white matter changes) on preoperative brain magnetic resonance imaging is common in patients having aortic arch surgery. This study sought to determine whether it is associated with adverse neurologic outcome in the postoperative period. Data were collected from a retrospective chart review of 142 patients in whom total aortic arch replacement was planned at the Cleveland Clinic between April 2000 and December 2004. All patients had preoperative brain magnetic resonance imaging evaluation. Leukoaraiosis severity was rated semiquantitatively using the Schelten's scale. Postoperative neurologic injuries were investigated by clinical examination and appropriate neuroimaging. They were stratified as type 1 (focal ischemic stroke) and type 2 (nonfocal neurocognitive changes, generalized seizures) injuries. The following were independent predictors of type 1 neurologic injury: age (odds ratio 1.06 [1.01-1.13], P = .02) and moderate to severe aortic atheroma (odds ratio 4.4 [1.4-9.7], P = .012). Total white matter scores (odds ratio 1.16 [1.06-1.27], P = .002) and higher preoperative hemoglobin A1c levels (odds ratio 1.8 [1.00-3.50], P = .05) were significantly associated with type 2 neurologic injuries. Survival was 96%, and 4.2% had persistent focal neurologic deficits at the time of hospital discharge. Leukoaraiosis is a significant independent predictor of nonfocal postoperative neurologic morbidity following aortic arch replacement surgery. Preoperative evaluation with magnetic resonance imaging allows identification of a patient subgroup at risk and implementation of strategies aimed at improving neurologic outcome.