Aortic dissection with no entry or false lumen flow was recently identified as intramural hemorrhage of the aortic wall (IMH). Analysis of the literature revealed 209 cases of in vivo diagnosed IMH reflecting 17% of all dissections, whereas in postmortem studies this condition is found in 4-13%. Transesophageal echocardiography, computed tomography, magnetic resonance imaging and aortography (to rule out dissection) have been applied for diagnosing IMH in 57, 49, 43 and 38% of the cases, respectively. However, diagnostic accuracy of each modality is not available to date. In 34%, IMH involves the ascending aorta (type A). The average age of patients with IMH ranges between 55 and 65 years; 65% are males. In 12%, IMH was associated with abdominal aortic aneurysm. With 87%, arterial hypertension is the predominant risk factor for IMH irrespective of its location. As suggested by the term "mediastinal apoplexy" IMH may--similar to cerebral apoplexy--result from hypertensive rupture of the vasa vasorum in the aortic media. With 97%, the majority of patients present with acute chest or back pain similar to classic dissection. Mediastinal widening is found in 83%; signs of hemothorax/pleural effusion are present in 38%, acute aortic regurgitation in 26%, pericardial effusion in 23%, acute neurologic deficits in 12%, and pulse deficits in 5%. In 18%, IMH progresses to dissection and in another 15% to rupture. In 25% and 28%, respectively, dissection and rupture occur in the ascending aorta and in 12% and 9%, respectively, in the descending thoracic aorta. The 30-day mortality of IMH is 24% (36% with type A and 12% with type B IMH; p < 0.05). With surgical repair, mortality of type A IMH is lowered to 18% compared to 60% with medical treatment (p < 0.01). In contrast, with 8% mortality associated with medical treatment, prognosis of type B IMH is more favorable without surgical intervention, the latter associated with a 30-day mortality of 33% (p < 0.05). Thus, IMH is a potential precursor of dissection and should be managed like dissection with undelayed surgical intervention in patients with type A IMH and with medical treatment in type B IMH.