Each year hundreds of thousands of patients suffer from acute upper gastrointestinal bleeding (UGIB) [1], which by definition arises from a site proximal to the ligament of Treitz. Etiological factors include peptic ulcer disease, gastritis, gastroesophageal varices, and Mallory-Weiss tears. Less common causes are marginal ulcers, esophagitis, gastric cancer, aorto-enteric fistulas, hemobilia, AV malformations (Fig. 1), and Dieulafoy lesions [2,3]. Peptic ulcer disease, including gastric/duodenal ulcers (Fig. 2) and erosive esophagitis/gastritis (Fig. 3), is the source of bleed 50-75% of the time [1,2,4,5]. The incidence of esophageal varices is 10-30%, Mallory-Weiss tears 4-13%, AVMs 2-4%, malignancies 1-5%, and Dieulafoy lesions 1-2% [5]. © 2010 Springer-Verlag New York.