Spontaneous rupture of the ascending aorta is a life-threatening condition requiring immediate intervention. The rupture usually leads to sudden death as a result of hemopericardium or hemothorax. The underlying histopathological condition in the cases described so far was mostly an atheromatous plaque. Some other rare underlying conditions were also described. We report a case of cystic medial necrosis Erdheim Gsell as a reason for fatal spontaneous rupture of the ascending aorta.