Asymmetric dimethylarginine (ADMA) was measured with the prediction that patients with elevated ADMA levels, depressed urinary nitrogen oxides and reduced FMVD might be more responsive to L-arginine therapy. A second aim of the protocol was to determine if the chronic enhancement of nitric oxide synthesis by L-arginine supplementation had an enduring effect on conduit vessel structure. The ankle brachial index, plethysmography, and MR perfusion imaging were performed at 0, 6 and 12 months on therapy, and at 1 month after cessation of therapy.