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 hat 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 he patient with border-zone infarct was discharged home with no symptoms 3 months after surgery.