When we surgically treat cases for dissecting aortic aneurysm with an inheritable connective tissue disorder like Marfan's syndrome, we should choose the surgical procedure carefully, paying paticular attention to whether to extend the operation, because there is every possibility that the lesion might be progressive. A 41-year-old woman with Marfan's syndrome, type A chronic aortic dissection, rapidly dilating to 80mm in diameter, and with aortic valve regurgitation was operated on with a total aortic arch replacement and the modified Bentall procedure. In the procedure, the aortic root and valve were replaced with a composite graft with a prosthetic mechanical valve, and the coronary arteries were reconstructed by direct anastmosis. In this case, the infrarenal abdominal aorta had already dilated to 40mm in diameter. In many cases with Marfan's syndrome, it was reported that the lesion was progressive and the residual dissection or new aneurysm would usually dilate and eventually rupture postoperatively. Reoperation involve a high risk. With those factors in mind, we chose total aortic replacement, including the distal aortic arch, to where the dissection would not extend. The most important thing for patients with Marfan's syndrome is the development of new or reccurrent problems. We consider that the operation designed to dissect aortic aneurysm for those patients should be performed as extensively in the surgical field as possible.