Peripheral arterial disease is a fundamental consideration in the patient presenting with a diabetic foot. Although broad in context, it is only part of the overall alteration in vascular structure and function characterized by two distinct pathologic processes: a nonocclusive microcirculatory impairment involving the capillaries and arterioles of the kidneys, retina, and peripheral nerves and a macroangiopathy manifesting as atherosclerotic lesions of the coronary and peripheral arterial circulation. The former is relatively unique to diabetes and is best described as an accelerated microangiopathy rather than an occlusive process. In addition to its well-recognized contribution to the development of diabetic neuropathy, retinopathy, and nephropathy, this microvascular dysfunction is also of paramount importance in the diabetic foot.