To determine the nature of neurologic dysfunction after deep hypothermic circulatory arrest during aortic arch surgery, we reconsidered the cases of 154 patients who had undergone aortic arch surgery (either of the ascending or transverse aorta, or both) between November 1993 and July 1999. Temporary postoperative neurologic dysfunction was seen in 9 patients (5.8%), and another 3 patients (1.9%) experienced stroke. Patients with temporary neurologic dysfunction had no new infarct and were discharged home with no residual symptoms. Computed tomographic scans revealed that 2 patients with stroke had multiple infarcts in the brainstem, and the 3rd had bilateral border-zone infarcts. The patients with brainstem infarcts died on postoperative days 7 and 15, and the patient with border-zone infarct was discharged home with no symptoms 3 months after surgery. Univariate analysis revealed that patients with neurologic deficits had significantly higher rates of history of hypertension, concomitant coronary artery bypass grafting, cardiac ischemia times longer than 90 minutes, and chronic renal failure. A multivariate logistic regression analysis revealed that the significant preoperative variables associated with neurologic deficits were a history of hypertension and a cardiac ischemia time longer than 90 minutes. Deep hypothermic circulatory arrest is a safe and useful technique for protection of the brain during surgery for complex aortic problems. In future, some patients at extreme risk for perioperative neurologic complications might be offered novel neuroprotective agents, in combination with deep hypothermia.