Background-The proper treatment option for patients with type A intramural hematoma (IMH), a variant form of classic aortic dissection (AD), remains controversial. We assessed the outcome of our institutional policy of urgent surgery for unstable patients and initial medical treatment for stable patients with surgery in cases with complications. .56). The 1-, 2-, and 3-year survival rates of IMH patients were 87.6Ϯ3.6%, 84.9Ϯ3.7%, and 83.1Ϯ4.1%, respectively. There was no statistical difference of overall survival rates between patients with IMH and surgically treated AD patients (Pϭ0.787). Conclusions-The clinical outcome of IMH patients receiving treatment by our policy was comparable to that of surgically treated AD patients. However, adverse clinical events were not uncommon with medical treatment alone, and initial aorta diameter and hematoma thickness may identify patients who might benefit from urgent surgery.