Acute mesenteric ischemia is becoming an increasing cause of death in old patients with generalized atherosclerosis. Pathogenetically, this condition presents as poor splanchnic perfusion, with or without occlusion of the major visceral vessels. Because the patient manifests such nondescript abdominal pain and the physical examination reveals few abdominal signs, it is therefore extremely difficult to make an accurate diagnosis in the early stage of the disease. Furthermore, laboratory studies and X-ray examinations are usually noncontributory. It is therefore necessary to keep this lesion in mind, whenever examining the old patient with severe unexplained abdominal pain. Selective arteriography is essential for differentiating occlusive ischemia from non-occlusive, however, the recent advances in medical imaging and minute flowmetry make it possible to detect intestinal lesions and the state of visceral perfusion, transcutaneously, in the early stage of the disease. Emergency revascularization is mandatory for an occlusive lesion, but it is not indicated in the early stage of non-occlusive disease, and requires support of cardiac failure, hypovolemia, septic shock and lowered splanchnic perfusion.