A 68-year-old woman in whom a thoracic aortic dissection (DeBakey type III) had been followed up for 6 years was admitted to our hospital with a complaint of chest pain. A graft replacement of the descending thoracic aorta was performed. A communication between the second and third channels was detected intraoperatively. Nine cases of three-channeled aortic dissection whose third dissection existed within the outer wall of the second one were previously reported, and 4 of them had a communication between the two false channels.