Population aging has been accompanied by a growing burden of chronic medical conditions. Elderly individuals represent an increasing proportion of the total number of patients with chronic kidney disease, acute renal failure, and end-stage renal disease. In addition, age-related changes in the kidneys and other organ systems predispose the older person to disturbances in fluid and electrolyte balance, which exacerbate renal dysfunction. This article reviews the evolving epidemiology of renal disorders among the elderly and summarizes evidence put forward to explain this phenomenon.