This is a Phase I Safety/Toxicity and Biological Efficacy trial administering the AdVEGF121 vector to the lower limb of individuals with peripheral arterial disease. The hypothesis is that delivery of this vector will allow for expression of VEGF and result in angiogenisis in the lower limbs. This will then hopefully improve blood flow and reduce they symptoms of claudication and critical limb ischemia. The aims of the study were to: 1) Determine the dose - dependent safety/toxicity of direct administration of the vector AdVEGF121 to the ischemic lower limb; 2) To demonstrate whether the direct administration of AdVEGF121 to the lower limb will induce growth of collateral vessels and improve blood flow and function in the region of ischemia.