Chronic kidney disease (CKD) is now recognized as a major public health problem. The National Kidney Foundation has recently classified stages of declining kidney function. However, the health risks that accompany each CKD stage have not been quantified. In addition, the significance of CKD with aging is unknown, and reasons for the excess prevalence of end-stage renal disease (ESRD) in African Americans are unclear. These problems can be addressed by increasing knowledge about the health outcomes associated with each CKD stage across demographic groups. This study has the following specific aims: (1) To estimate rates of cardiovascular disease events, ESRD and death among patients with CKD and test for differences in event occurrence by age, sex and race/ethnicity; and (2) To estimate the progression of CKD to subsequent stages and test for differences in progression by age, sex and race/ethnicity. In order to accomplish these aims, we propose a retrospective study of persons with CKD using existing electronic data. Study subjects are members of Kaiser Permanente Southern California, which is a large, integrated, prepaid health plan. Data on more than 100,000 current and past members with CKD who are identified using objective, clinical criteria developed for a case-identification database will be analyzed. CKD stage is defined by national guidelines using urinary protein and GFR, which is estimated from serum creatinine, age, sex, and race using established prediction equations. Information from this study will be of the scope and quality to allow us to assess the national guidelines for staging CKD. Further, information from this study may guide health care providers to better inform patients with CKD about health risks, to identify high-risk groups for prevention services, to better plan for ESRD therapy, and to guide resource allocation for populations with CKD. Researchers may use this information to generate hypotheses and plan studies that include subjects with CKD.