Hyperglycemia can promote vascular complications by multiple mechanisms, with formation of advanced glycation endproducts (AGEs) and increased oxidative stress proposed to contribute to both macrovascular and microvascular complications. Many of the earliest pathologic responses to hyperglycemia are manifest in the vascular cells that directly encounter elevated blood glucose levels. In the macrovasculature, these include endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). In the microvasculature, these include ECs, pericytes (in retinopathy), and podocytes (in renal disease). Additionally, neovascularization arising from the vasa vasorum may promote atherosclerotic plaque progression and contribute to plaque rupture, thereby interconnecting macro- and microangiopathy.