 - Clinical diagnosis of PAD, secondary to atherosclerosis, in both lower limbs, confirmed by objective evidence: An ankle-brachial index ABI of 0.90 at rest in at least 1 lower limb Note: The index limb must be 0.90 at rest.; The ABI after exercise must be reduced by 20 from the ABI at rest in the index leg the most symptomatic leg during the treadmill testing. The post-exercise ABI will also be performed on the other leg if the resting ABI 0.90. A patient may be eligible for the study with a resting ABI in the non-index limb 0.90 if: a. The post-exercise ABI in the non-index leg is also reduced by greater than or equal to 20 OR; b. A medically significant stenosis defined as 50 of a femoropopliteal or infrapopliteal artery is present, as documented via an imaging study such as MR, conventional angiography, duplex ultrasound, or CT; If the ABI cannot be measured in either leg due to non-compressible arteries, then a toe-brachial index TBI of 0.70 may be used in its place to confirm PAD. 