Two patients with DeBakey IIIb dissecting aortic aneurysms were treated with transluminally placed endovascular stent grafts. Surgery was required for both patients because the false lumens were not thrombosed for several months. Stent graft devices composed of several units of self-expandable Z stents covered with ultra-thin woven Dacron were inserted through 18 Fr sheathes via femoral arteries. The stent grafts were deployed successfully and blood flow into the false lumens was reduced immediately and finally thrombosed without blood leakage from the entries. The endoluminal stent graft treatment is minimally invasive operation in comparison with former surgical operations, and is useful for aortic aneurysms especially in high risk patients. However, improvement of the stent graft devices, including the delivery systems such as the dilator, sheath and pushing rod, which are incomplete, and developing better devices, is required to reduce delivery failure and to make the stent graft treatment more reliable.