There have been few reports of an aberrant right subclavian artery in patients with aortic dissection. The diagnostic and therapeutic implications of the association of these two abnormalities are important and potentially ominous. Two patients with extensive type III dissections of the thoracic and abdominal aorta are described. In one patient, extension of the dissection into the aberrant right subclavian artery led to eventual exsanguination into the esophagus. In the second patient, cross-clamping of the abdominal aorta proximal to the left subclavian artery at surgery resulted in complete cutoff of blood supply to both vertebral arteries and the patient's subsequent demise.