Finally, the importance of phosphorus control for patients with CKD has traditionally been to prevent bone disease. More recently it is recognized that poor phosphorus control correlates with cardiovascular disease, of which patients with CKD carry an enormous burden. Similarly, there has recently been much attention to circulating endothelial cells (CECs) as a novel marker for cardiovascular risk in this population. While the ultimate test would be to determine if controlling phosphorus impacts on cardiovascular events, that is beyond the scope of this project. Therefore, we propose to measure levels of CECs as an intermediary step toward cardiovascular events, in correlation to phosphorus intake.