This review presents the current evidence concerning timing of upper endoscopy in patients with suspected peptic ulcer bleeding. These patients should receive endoscopy within 24 hours after hospitalization in order to decrease the need of surgical haemostasis, risk of rebleeding and duration of hospital stay. In case of suspected serious bleeding and bloody nasogastric aspirate therapeutic endoscopy within 12 hours is beneficial in further reduction of length of hospital stay and need for blood transfusion. Early intensive resuscitation is presumably more important than early endoscopy in most patients.