Rupture of the ascending aorta may follow thoracic trauma or complicate an aortic aneurysm or acute dissection. It is otherwise extremely rare. The authors report a case of spontaneous rupture of the ascending aorta occurring in a patient with a pre-existing incomplete rupture of the ascending aorta, and treated surgically. The clinical presentation was of acute dissection with pericardial effusion. This diagnosis was excluded by aortography with multiple views which showed abnormalities of the aortic wall: an abnormal notch, continuity of the internal wall and extravasation of the contrast medium. These abnormalities are often minimal but should be recognised and surgery proposed as this is the only chance of a favourable outcome.