Acute nonvariceal upper gastrointestinal (UGI) hemorrhage is a frequent complication associated with significant morbidity and mortality. The most common cause of UGI bleeding is peptic ulcer disease, but the differential diagnosis is diverse and includes tumors; ischemia; gastritis; arteriovenous malformations, such as Dieulafoy lesions; Mallory-Weiss tears; trauma; and iatrogenic causes. Aggressive treatment with early endoscopic hemostasis is essential for a favorable outcome. However, severe bleeding despite conservative medical treatment or endoscopic intervention occurs in 5-10% of patients, requiring surgery or transcatheter arterial embolization. Surgical intervention is usually an expeditious and gratifying endeavor, but it can be associated with high operative mortality rates. Endovascular management using superselective catheterization of the culprit vessel, «sandwich» occlusion, or blind embolization has emerged as an alternative to emergent operative intervention for high-risk patients and is now considered the first-line therapy for massive UGI bleeding refractory to endoscopic treatment. Indeed, many published studies have confirmed the feasibility of this approach and its high technical and clinical success rates, which range from 69 to 100% and from 63 to 97%, respectively, even if the choice of the best embolic agent among coils, cyanaocrylate glue, gelatin sponge, or calibrated particles remains a matter of debate. However, factors influencing clinical outcome, especially predictors of early rebleeding, are poorly understood, and few studies have addressed this issue. This review of the literature will attempt to define the role of embolotherapy for acute nonvariceal UGI hemorrhage that fails to respond to endoscopic hemostasis and to summarize data on factors predicting angiographic and embolization failure.