Objective: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a potentially life-saving intervention. However, recent reports of associations with limb loss and mortality have called its safety into question. We aimed to evaluate patient and hospital characteristics associated with major amputation and in-hospital mortality among patients undergoing REBOA for trauma., Methods: The National Trauma Data Bank (2015-2017) was queried for patients presenting to trauma centers and treated with REBOA. We included REBOA performed on hospital day 1 in patients who survived 6 or more hours from presentation. Univariable and multivariable analyses evaluated associations with major amputation and in-hospital mortality., Results: A total of 316 patients underwent REBOA and survived in the acute period after presentation. Overall, mean age was 45 ± 20 years and the majority were male (73%) and White (56%). Most patients presented to level I trauma centers (72%) after blunt injuries (79%) with an average Injury Severity Score (ISS) of 31 ± 15, indicating major trauma. In 15 patients (5%), there were 18 major amputations-7 above knee and 11 below knee. A subgroup of 11 amputations were either traumatic amputations (73%) or mangled limbs requiring amputation within 24 hours (27%). Of the remaining amputations, 71% were associated with ipsilateral vascular or orthopedic lower extremity injuries of serious to severe Abbreviated Injury Scale severity. Comparing patients with amputations with those without amputations, there were no significant differences in patient demographics, comorbidities, or hospital characteristics. During hospitalization, patients requiring amputation more frequently received open peripheral vascular interventions (40% vs 10%; P = .002), underwent similar numbers of endovascular interventions (6.7% vs 4.7%; P = .5), and more often developed compartment syndrome (13% vs 2%; P = .04). Overall, there were 110 deaths (35%). The major amputation prevalence was similar between patients who died vs those who survived (3.6% vs 5.3%; P = .5). In multivariable analysis, prehospital cardiac arrest (odds ratio [OR], 8.47; 95% confidence interval [CI], 1.47-48.66; P = .02), penetrating vs blunt trauma (OR, 5.5; 95% CI, 1.05-28.82; P = .04), decreased Glasgow Coma Scale score (OR, 1.18; 95% CI, 1.05-1.32; P = .01), older age (OR, 1.06; 95% CI, 1.03-1.10; P < .001), and increased Injury Severity Score (OR, 1.05; 95% CI, 1.0-1.1; P = .03) were associated with higher mortality., Conclusions: The majority of major amputations in patients undergoing REBOA were secondary to the initial traumatic mechanism. Injury type and severity, as well as initial hemodynamic derangements, are associated with mortality after REBOA. Despite concerns about prohibitive limb complications of REBOA, baseline injuries seem to be the primary cause of limb loss, but further prospective analysis is needed., (Copyright © 2021 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)