One hundred and ten patients with critical leg ischemia and no surgical option will be included. A bone marrow harvest (500 mL under general anaesthesia) is performed and BM-MNC are separated and concentrated (30 mL) for all included patients. For half of them, the BM-MNC are implanted on the same day whereas the others are implanted with a placebo cell-product (30 mL saline with 4 ml peripheral blood). For these patients the BM-MNC are cryo-conserved. Only the cell therapy unit, neither the patient, nor the clinician, know whether BM-MNC or placebo is implanted. The main end point is the survival without major amputation 6 months after implantation. After this delay it is possible to use previously cryo-conserved BM-MNC. Likewise biological studies are performed on BM-MNC: flow-cytometry analysis of progenitor cells content, proteins and mRNAs expression, induced angiogenesis in animal models.