We report three cases of fatal retrograde dissection of the aortic arch after exclusion-bypass with metal clamps according to Carpentier's thromboexclusion method. All three patients were male, aged 59, 66, and 73 years. Initial operative indications were chronic dissections in two cases and atheromatous aneurysm of the descending thoracic aorta in the other. Two of these patients were operated on in an emergency setting for a ruptured aneurysm. In all three cases, an extraanatomic bypass between the ascending aorta and abdominal aorta was performed as the first step: The proximal clamp was then placed distal to the origin of the left subclavian artery. Death occurred two hours, 12 hours, and eight days after operation, respectively. Autopsy revealed retrograde dissection initiating in the aortic arch and reaching the aortic ring as the cause of death. Pathological examination of aortic specimens confirmed that the dissections began just proximal to the site of clamping. To explain this complication, two etiologic factors, occurring either alone or together, have been postulated: postoperative hypertension and trauma to the aortic wall from the clamp.