In intensive care units, gastroduodenal ulcers may occur in a context of aggression or multiple organ failure or result from iatrogenic causes. Thus it is difficult to construct a unique theory of pathogenesis and consequently define a precise therapeutic target. The mechanisms which disrupt the protective digestive mucosa occur as the consequences of "intensive care stress". Factors favoring the development of these stress lesions of the gastroduodenal mucosa include multiple trauma, surgery, extensive burns, acute renal failure, acute respiratory failure, shock or severe infection. These factors should be distinguished from the recently defined risk factors for hemorrhage: defective hemostasis, respiratory failure requiring prolonged ventilation assistance. The first objective in preventing stress bleeding in the intensive care unit is thus to correct these favoring factors. The only target for drug prophylaxy is gastric oversecretion which can be well controlled with anti-H2 agents but also with sucralfate. These often expensive treatments improve the rate of complications but do not decrease overmortality related to this complication. Curative treatment is difficult in these severely ill patients. It is thus necessary to define high-risk patients who could benefit significantly from these treatments.