[en] Acute lower limb ischemia, with sudden interruption of tissue perfusion, is a medico-surgical emergency. An early diagnosis is a prerequisite for optimal management. Diagnosis is mainly based on clinical data. Complementary investigations have a limited place, and should not unnecessarily delay the treatment. There are two categories of acute arterial, non-traumatic occlusion: embolism and thrombosis of an atherosclerotic vessel. The distinction between these two entities is not always evident, since ischemia can be the consequence of an arterial embolism in a diseased atherosclerotic artery. We discuss the clinical aspects and the causes of acute lower limb ischemia. The prognosis, outcome and therapeutic management are determined by the cause of the acute arterial obliteration.