Despite advances in revascularization techniques, limb salvage and relief of pain cannot be achieved in many diabetic patients with diffuse peripheral vascular disease. Our objective was to determine the effect of intramuscular administration of phVEGF165 (vascular endothelial growth factor gene-carrying plasmid) on critical limb ischemia (CLI) compared with placebo (0.9% NaCl). A double-blind, placebo-controlled study was performed in 54 adult diabetic patients with CLI. The primary end point was the amputation rate at 100 days. Secondary end points were a 15% increase in pressure indices (ankle-to-brachial index and toe-to-brachial index), clinical improvement (skin, pain, and Quality of Life score), and safety. In patients (n=27) treated with placebo versus phVEGF165-treated patients (n=27) the following results were found: 6 amputations versus 3 (p=not significant [NS]); hemodynamic improvement in 1 versus 7 (p=0.05); improvement in skin ulcers, 0 versus 7 (p=0.01); decrease in pain, 2 versus 5 (p=NS); and overall, 3 versus 14 responding patients (p=0.003). No grade 3 or 4 adverse effects were seen in these patients. We conclude that this small, randomized gene therapy study failed to meet the primary objective of significant amputation reduction. However, significant and meaningful improvement was found in patients treated with a VEGF165-containing plasmid. There were no substantial adverse events.