Acute intramural haematoma of the ascending and descending aorta was diagnosed by CT in a patient with chest pain and suspected thoracic aortic dissection. Surgical mortality from aortic replacement in this condition is high. Intramural haematoma has an unpredictable course but studies suggest that resolution of haematoma carries a favourable prognosis against further complications. Serial MR examinations over the next 6 weeks demonstrated resolution of the haematoma. This information influenced the decision not to undertake surgery and the patient was continued on antihypertensive medication. Serial MR examination is a safe and reliable method of monitoring the progress of intramural haematoma and thus guiding difficult treatment decisions.