Estimated glomerular filtration rate (eGFR) is now commonly reported by clinical laboratories. Here, we review the performance of current creatinine and cystatin C-based estimating equations as well as demonstration of their utility in public health and clinical practice.Lower levels of GFR are associated with multiple adverse outcomes, including acute kidney injury and medical errors. The new Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation improves performance and risk prediction compared with the Modification of Diet in Renal Disease study equation. Current cystatin C-based equations are not accurate in all populations, even in those with reduced muscle mass or chronic illness, in which cystatin C would be expected to outperform creatinine. eGFR reporting has led to a greater number of referrals to nephrologists, but the increased numbers do not appear to be excessive or burdensome. The Modification of Diet in Renal Disease study equation appears to be able to provide drug dosage adjustments similar to the Cockcroft-Gault equation.Estimated GFRs and their reporting can improve and facilitate clinical practice for chronic kidney disease. Understanding strengths and limitations facilitates their optimal use. Endogenous filtration markers, alone or in combination, which are less dependent on non-GFR determinants of the filtration markers, are necessary to lead to more accurate eGFRs.