Advances in surgical technique have improved early survival after surgery of the ascending aorta. However, follow-up data document serious late complications, mainly evolutive peri-prosthetic false aneurysms. Magnetic resonance imaging (MRI) has proved to be highly effective for monitoring these complications. This study evaluates 10 years of experience with routine MRI for follow-up. Since January 1988, 114 patients with replacement of the ascending aorta either for type A acute dissection (group I, 45 patients) or aneurysms (group II, 69 patients) were followed up with annual MRI. Prosthetic replacement was either limited to supra-coronary ascending aorta (45%, 51/114) or extended to the aortic root and/or the aortic arch (55%). Biological glue was always utilized. MRI focused on peri-prosthetic haematoma, analyzing signal intensity changes and volume augmentation for early detection of false aneurysms, and on persistent residual dissection with or without evolutive aortic aneurysm distant to the prosthesis. Peri-prosthetic hematomas were almost equally found in both groups (26 (58%) in group I and 42 (61%) in group II) and were detected within the first year. Peri-prosthetic false aneurysms developed in 15 patients (group I, seven; group II, eight) as a complication of pre-existing hematomas and were indicated for elective reoperation. Forty-three (96%) of patients in group I had persistent residual dissection. Five patients in group I and two in group II needed reoperation for evolutive aortic aneurysm. In total, 22 of 114 (19%) patients were reoperated on during follow-up (12 (27%) in group I and ten (15%) in group II). Operative mortality was 13% (3/22). Freedom from reoperation at 1 year/5 years was: group I, 93%/84%; group II, 98%/88%. Peri-prosthetic haematoma occurs equally after aneurysm or dissection repairs and is a pre-existing condition for peri-prosthetic false aneurysm; biological glue or extended repair do not prevent late complications. Long-term MRI follow-up allows successful elective reoperation for life-threatened but asymptomatic patients.