An estimated 17% of the US adult population has chronic kidney disease (CKD) based on diagnosis criteria guidelines issued by the Kidney Disease Outcomes Quality Initiative in 2005. In addition to end stage renal disease (ESRD), patients with intermediate and higher stages of chronic kidney disease (stage 3b and higher, eGFR< 45 ml/min/1.73m2) are at greatly increased risk of hospitalization, cardiovascular events, and death. However the majority of CKD patients have mild disease (stage 3a; eEGR 45-59 ml/min/1.73m2). CKD is particularly prevalent in older patients. Concern has been raised that the new guidelines will lead to over-treatment of older patients. It has been argued that the GFR estimating equation is less accurate in older patients and that most of these patients have mild disease that is unlikely to progress. We characterized CKD in Health Partners patients, using data from a retrospective cohort of adults who developed hypertension over the years between 2000 and 2007. We considered patients having at least one creatinine measurement, using the first available measure. The proportions of patients according to eGFR category were 24.7% stage 1, 55.5% stage 2, 13.6% stage 3a, 4.7% stage stage 3b, 1.2% stage 5, and 0.3% stage 5. CKD prevalence increased appreciably with higher age. Additional analyses included the proportions of patients for whom eGFR declined, according to initial eGFR category and age.