Eleven patients underwent resection and graft replacement of ascending and aortic arch aneurysms. Retrograde cerebral perfusion was used during the procedures to minimize cerebral ischemia. Retrograde cerebral perfusion (15 degrees to 24 degrees C) was administered through the superior vena cava. The mean cerebral ischemic time was .35 minutes (range, 11 to 71 minutes). Throughout retrograde cerebral perfusion, blood samples were drawn from the innominate and left carotid arteries at 1, 5, and every 10 minutes thereafter for analysis of arterial oxygen content, total creatine kinase level, and creatine kinase BB fraction. All patients survived. All except 1 awoke neurologically intact. In this patient, electroencephalogram and transcranial Doppler studies conducted before circulatory arrest were consistent with embolic phenomena. There was no significant difference between the current group's intraoperative electroencephalograms and those of a similar historical group. Postoperative complications included transient renal failure, myasthenia gravis, cholecystitis, premature atrial contractions, atrial fibrillation, and vocal cord paralysis. The creatine kinase BB fraction range was 1.8 to 13.4. The increase of total creatine kinase level was due to MM fraction. Retrograde cerebral perfusion during circulatory arrest is a valuable adjunct for protecting the brain. The creatine kinase BB band was not a good marker to detect brain injury. With continued use of this technique and accumulation of a larger series, we may better define the role of retrograde cerebral perfusion in brain protection.