Thoracic aortic aneurysms and arch aneurysms are clinical challenges for the cardiothoracic surgeon. These patients need extensive preoperative workup and the correct operation needs to be chosen. Specific attention to potential complicating factor is paramount during case planning. There is much debate that surrounds the optimal cerebral protection during circulatory arrest including retrograde perfusion, selective antegrade perfusion, straight hypothermia, or a combination of these. Depending on the patient’s specific disease process and anatomy, different operations may be needed including the frozen elephant trunk. This chapter will go into great detail in outlining many different approaches to treating these complex patients.