Previously with a drastic prognosis, aortic dissection has extensively benefitted from advances in medical and surgical treatment, as well as progress in methods of investigation. While aortography is classically the reference special investigation, non-invasive methods now have a place of choice both during the acute phase (transthoracic and transesophageal echocardiography) and the chronic phase or for the purpose of post-operative monitoring (CT scan, magnetic resonance imaging). In an emergency context, the most important point is to diagnose a type A dissection, involving the ascending aorta, the treatment of which is surgical. In the majority of cases the diagnosis can now be made on the basis of transthoracic and transesophageal echocardiographic findings, which also enable identification of the site of the portal of entry, extension and concomitant lesions, all important features to be taken into consideration regarding surgical tactics.