Background: Focal contrast enhancement contained in the aortic intramural hematoma (FCE) on contrast-enhanced computed tomography (CT) is occasionally observed in patients with acute distal aortic intramural hematoma (IMH). Data are limited regarding its prevalence, fate and outcomes, and optimal treatment strategy needs to be established. Methods and Results: Among the registry data of acute aortic syndrome, patients with distal IMH who underwent repeated CT during medical treatment were selected. A total of 107 patients (mean age, 63짹11 years; 64.5% male) with distal IMH were enrolled for this analysis; CT and clinical follow-up durations were 29짹33 and 52짹36 months, respectively. FCE was present in 42 patients (group I, 39.3%), whereas the others showed no FCE (group 2). Except higher prevalence of hypertension in group 1 (78.6% vs. 56.9%, p=0.022), there was no difference of baseline characteristics including age, gender and diabetes between groups. Maximal aortic diameter was not different, but group 1 showed thicker hematoma (12.3짹3.6 vs. 10.1짹4.1 mm, p=0.006). Overall in-hospital mortality was 0.9% (1/107) and was not different between groups. Localized aortic dissection (AD) developed in 11 patients (10.3%) with significantly higher incidence in group 1 (21.4% [9/42] vs. 3.1% [2/65], p=0.002). FCE was the only variable associated with progression into AD (hazard ratio = 15.82, 95% confidence intervals = 1.952 – 128.236, p=0.01). The 7-year survival rates were not different between groups (77.7짹9.4% vs. 77.7짹5.8%, p=0.745). Patients with localized AD showed comparable survival compared to those without and only 1 patient needed an elective stenting. The maximal aortic diameter did not change significantly in patients who developed localized AD. Conclusions: FCE is frequently observed during acute stage of distal IMH and is associated with progression into typical AD. However, over-all prognosis is excellent and prophylactic surgical or endovascular intervention cannot be justified.