The advent of gastrointestinal endoscopy has allowed us to follow the morphologic results of severe stress on the gastrointestinal mucosa. It has become clear, however, that the presence of mucosal abnormalities does not always correlate with the presence of overt bleeding, or with the effect of bleeding on the overall outcome of such patients. In fact, the incidence of severe gastrointestinal hemorrhage, secondary to stress-related mucosal disease, has been decreasing over the past decade, as the care of these critically ill patients has improved. In patients who do have overt hemorrhage, however, the mortality rate is extremely high. It therefore remains the duty of the clinician to identify patients who are at high risk of having overt hemorrhage, and ensure that they receive adequate prophylactic therapy.