Acute mesenteric ischemia is not an isolated clinical entity, but a complex of diseases, including acute mesenteric arterial embolus and thrombus, mesenteric venous thrombus, and nonocclusive mesenteric ischemia. These diseases have common clinical features caused by impaired blood perfusion to the intestine, bacterial translocation, and systemic inflammatory response syndrome. There is substantial evidence that the mortality associated with acute mesenteric ischemia varies according to its trigger cause. Nonocclusive mesenteric ischemia is the most lethal form of the acute mesenteric ischemia, because of the poor understanding of its pathophysiology and its mild and nonspecific symptoms, which often delay its diagnosis. Mesenteric venous thrombosis is much less lethal than acute thromboembolism of the superior mesenteric artery and nonocclusive mesenteric ischemia. In this articles we presents an overview of acute mesenteric ischemia, based on the research. Although the mortality rates, in acute mesenteric ischemia, have remained high over the last few decades, accumulated knowledge on this condition is expected to improve its prognosis.