The search for a source of gastrointestinal bleeding is one of the most frequent indications for gastrointestinal endoscopy. The endoscopic search is associated with two distinct approaches. The first search serves to rule in a suspected diagnosis. The suspicion is usually based on characteristic signs and symptoms, past medical his- tory, clinical presentation, constellation of laboratory parameters, or pre-existing findings on radiologic ima- ging. The endoscopic search is focused on a single diag- nosis or short list of few differential diagnoses ordered by their declining probability of occurrence. Endoscopy serves as a test to confirm a high pre-test suspicion for a specific lesion. The second type of endoscopic search serves to rule out any bleeding source inside the gastro- intestinal tract.