The authors report a case of chronic dissection of the aorta discovered during the evaluation of disseminated intravascular coagulation. The first signs of bleeding occurred 4 years after the initial aortic trauma at the time of unclamping of the aorta during an aorto-coronary bypass. This case was characterised by the severity of coagulation abnormalities, the severe thrombocytopenia and that of platelet aggregation events.