Twenty-one patients were examined with MRI 0.5 to 200 months after surgical aortic dissection. The series included 15 type-I dissections, 1 type-II dissection and 5 complicated type-III dissections. MR images demonstrated the persistence of the intimal flap with patency of both the true and the false lumen in 17 cases, the complete obliteration of the false lumen in 1 case and the partial thrombosis of the false lumen in 3 cases. Coronary artery ostial reimplantation was depicted in all the patients who underwent this kind of surgery; in 1 case, a small hematoma was present at the site of reimplantation. In 3 patients, an organized hematoma was seen between the prosthetic graft and the native aortic wall; in 1 case the aortic lumen was markedly reduced, while in the extant 2 cases, signal intensity features were suggestive of subacute hematoma due to prosthetic graft degeneration. Seven patients underwent two MR exams: the first one immediately after surgery (in most cases) and the second one at 3-11 months. Aortic diameter progressively increased in 4 patients, 3 of them with Marfan syndrome. In conclusion, MRI proved an accurate technique to assess aortic size beyond the prosthetic graft and to demonstrate the residual dissecting process and the postoperative problems in the prosthetic conduit.