Thirty-five consecutive patients with aortic arch aneurysm who required surgical reconstruction were operated on with the aid of extracorporeal circulation between February 1985 and December 1993. Nineteen patients (54.3%) were treated with hypothermic circulatory arrest (HCA) (Group A) and 16 (45.7%) (Group B) with HCA and selective cerebral perfusion (SCP) through the carotid arteries. Preoperative characteristics didn't show any significant differences between the two groups: mean age was 58.7 +/- 12 vs 62.1 +/- 7, p = ns, male sex 73.6% vs 75%, p = ns; atherosclerotic aneurysms were 57.8% vs 43.7%, p = ns; Type A dissections 42.2% vs 56.3%, p = ns and emergency operation were 68.4% vs 43.7%, p = ns in Groups A and B respectively. For SCP, blood was infused initially at a rate of 200-300 ml/min, maintaining the 30-40% of cerebral blood flow in normothermia, successively, with the aid of transcranial Doppler sonography (TDS) SCP-flow was improved to 500-1000 ml/min. The MHz pulsed TDS was used to measure the middle cerebral artery flow velocity in deep hypothermia before the arrest, in order to adjust the SCP flow during the HCA. In all patients we used open aortic anastomosis; in two cases an extraanatomical ascending-descending aorta was required, and in other two the "elephant trunk" technique was used in case of combined aortic arch and descending aneurysms. The HCA times were similar in the two groups 47.5 +/- 22 vs 47.7 +/- 78, p = ns. Early deaths occurred in 5 patients of the Group A (26.3%) and in 3 patients of the group B (18.7%), p = ns.(ABSTRACT TRUNCATED AT 250 WORDS)