This study is a double-blind study to evaluate the efficacy and safety of NV1FGF, a pCOR plasmid constructed by inserting the gene coding for the FGF compared to placebo in patients with severe Peripheral Arterial Occlusive Disease, Fontaine's stage IV. The efficacy was assessed by the complete healing of at least one ulcer in the treated limb, 25 week post-baseline and secondary by the rate of amputation and death.