This chapter discusses the diagnosis, evaluation and management of acute mesenteric ischemia. The diagnosis should be considered in those older than 50 years, presenting with nonspecific abdominal pain and risk factors for the disease. The physician must have a high index of suspicion as the history of the disease may be difficult to obtain. The chapter lists clinical presentations of the subtypes of mesenteric ischemia. Emergent laparotomy is indicated, especially if signs of peritonitis are present. Surgery is generally the standard of care for mesenteric arterial embolism and thrombosis. Surgery is done to determine the extent of damage, to find the underlying cause, to revascularize viable bowel, and to resect infarcted bowel. Second-look procedures are often performed 24-48 hours after the initial surgery in order to restore continuity and assess extension of ischemia to ensure that at-risk or ischemic bowel is not used for the final anastomosis.