Clinical rebleeding is usually defined as vomiting of red blood, hemodynamic instability or drop in the hemoglobin level after initial stabilization. These clinical features appear only after a significant amount of blood has been lost. There is, at present, no reliable method of detecting rebleeding in a timely fashion. If there is a reliable early warning system, analogous to ECG monitoring for arrhythmia in patients who has had a myocardial infarction, we may be able to intervene in time to preempt the harmful effects of further major blood loss in a patient who has already bled from the ulcer.