The National Kidney Foundation developed and oversees the Kidney Disease Outcomes Quality Initiative, a process that develops clinical practice guidelines in nephrology. Recent guidelines address the evaluation, classification, and stratification of chronic kidney disease (CKD). These guidelines provide, for the first time, a standard definition of CKD, classification of its stages, and suggestions for appropriate laboratory measurements for the assessment of kidney function. Also discussed are the association of level of kidney function with systemic complications that develop during CKD, and the risk of loss of kidney function and development of cardiovascular disease in CKD.