The incidence of end stage renal disease in patients who have not experienced a classic primary renal disease is dramatically increasing. Chronic kidney disease (CKD) in these patients is due to diabetes, mostly type 2, hypertension and generalised atherosclerosis. As these patients are frequently diagnosed as having renal function impairment only in the late phase, more effort should be undertaken to diagnose them earlier, that is, at a time when renoprotective measures can still be undertaken. For that purpose, measurement of the estimated glomerular filtration rate (GFR) might be helpful. To properly interpret those measurements, however, we need to be aware of the pros and cons of the use of formulas to estimate the GFR. Most likely, a better way to detect subjects at risk of CKD in the early phase is screening by dipstick proteinuria or preferably by testing for (micro-) albuminuria. Because microalbuminuria not only indicates increased renal but also enhanced cardiovascular risk, the benefits of such screening programmes may have a much greater affect than only preventing renal disease.