Treatment of thoracoabdominal aortic aneurysms has traditionally been by means of open surgery, but in recent years endovascular approaches have emerged as a viable and perhaps superior alternative. Some confusion appears to exist in discussions in the literature regarding the exact definition of the various types of thoracoabdominal aneurysm depending on whether open or endovascular repair is undertaken, with some authors comparing the preoperative extent of disease and others comparing the degree of aortic coverage required. Accurate preoperative planning and meticulous implantation technique are critical to successful outcomes with the endovascular approach. This study discusses the anatomical classification of type IV thoracoabdominal aneurysms as applied in open and endovascular surgery and outlines the authors' approach to the critical preoperative planning of endografts used to treat these aneurysms. The authors describe their techniques used to implant these devices, whether they consist of fenestrated or branched components, and some of the mechanisms by which minimization of complications such as spinal cord ischemia is sought.