Because survivors of thoracic aortic dissection require follow-up to detect prognostic factors such as intimal tears, persistent flow in the false lumen, and complications associated with grafts, we compared transesophageal echocardiography (TEE) with magnetic resonance imaging (MRI) prospectively in 14 patients 1 year after their initial examination. Residual dissection was identified by both techniques in 11 patients. Flow and/or thrombus in the false lumen were detected by TEE in 10 (91 %) and 6 (55%) patients, respectively, and by MRI in 9 (82%) and 5 (45%), respectively (p = NS); more tears were detected by TEE (2.5 +/- 1.4 per patient vs 0.2 +/- 0.4; p < 0.005). Satisfactory delineation of a graft in the ascending aorta was noted in all 8 (100%) of the surgically treated patients by TEE compared with 4 (50%) by MRI (p < 0.005). The upper ascending aorta was visualized clearly in fewer patients by TEE than by MRI (7 [50%] vs 13 [93%]; p < 0.05), as were the origins of the head and neck vessels (10 [71%] vs 13 [93%], p = NS). We conclude that TEE and MRI are both suitable techniques for the follow-up of patients with aortic dissection. TEE is more sensitive in identifying prognostic factors. MRI has a complementary role, particularly in visualization of the upper ascending aorta and the head and neck vessels.