To investigate predictors of intervention of acute type B aortic penetrating ulcer (PAU) and intramural hematoma (IMH). We conducted a retrospective chart review of all patients admitted for acute type B PAU or IMH in a tertiary referral hospital. Indications to intervention were "complicated" (rupture, impending rupture, malperfusion) or "high risk for unfavorable outcome" (refractory hypertension and/or pain despite best medical treatment, morphologic aortic evolution, transition to a new aortic syndrome, or increase in IMH/PAU depth >5 mm) during the acute/subacute phase. The primary outcomes were overall mortality, aortic-related mortality, and freedom from intervention. Time-dependent outcomes were estimated with Kaplan-Meier curves. Cox proportional hazards models were used to identify predictors of intervention and mortality. There were 54 acute aortic syndromes, 37 PAUs and 17 IMHs. Mean age was 69±14 years and 33 patients (62.2%) were male. Six (11.5%) patients had complicated aortic syndromes and underwent urgent repair. Two (3.7%) additional patients developed an impending rupture during the acute phase. Eleven (21.1%) patients were classified as at "high risk" during the initial hospitalization. Overall, 22 (40.7%) patients required an aortic intervention during the initial admission (n=16, 72.7% during the acute phase; n=6, 27.3% during the subacute phase). In-hospital mortality was 5.5% (1 PAU and 2 IMH), and was aorta-related in all cases. For IMH, disease extension in >3 aortic zones (HR 1.94, 95%CI 1.17-32.6; P=.038) and presence of ulcer-like projections (ULPs) (HR 1.23, 95%CI 1.02-9.41; P=.042) were associated with the need for intervention. There were no aortic-related deaths or intervention during the chronic phase. PAU width > 20 mm (HR 1.68, 95%CI 1.07-16.08; P=.014), PAU depth >15 mm (HR 6.74, 95%CI 1.31-34.18; P=021), PAU depth/total aortic diameter >0.3 (HR 4.31, 95%CI 1.17-20.32; P=.043), and location at the level of the paravisceral aorta (HR 2.24, 95%CI 1.23-4.70; P=.035) were significantly associated with need for intervention. Six additional (16.2%) PAUs required intervention during the chronic phase owing to PAU growth. Maximum aortic diameter >35 mm was significantly associated with intervention (HR 1.45, 95%CI 1.00-2.32; P=.037). Acute symptomatic type B IMHs and PAUs are characterized by a high risk of complications during the first month from presentation. Morphologic features associated with intervention were IMH with ULPs or extension in more than 3 aortic zones, as well as PAUs with depth>15 mm, width >20 mm, or depth/aortic diameter ratio>0.3. A strict follow-up protocol or consideration for early intervention within 30 days from presentation should be taken into account for these high-risk patients. During the chronic phase imaging follow-up is particularly important for PAUs in order to identify progression to saccular aneurysms.