Clinical symptoms are variable and prognosis poor in patients with dissecting aneurysm of the ascending or descending aorta. Dissecting aneurysm of the ascending aorta is almost always an acute condition with limited survival, since most patients die in the first few days from rupture into the pericardium or thorax. Surgical repair under controlled hypotension should be initiated. Aneurysm of the descending aorta can be an acute complication of hypertension or a more chronic and often unrecognized condition. The early and late prognosis of this group is far better, and hypotensive treatment should be initiated. Secondary re-entry is not unusual. Surgical repair is only considered if the aneurysm extends despite reduction of blood pressure to normal.