Aging is a normal degenerative biologic process that affects many organs, of which the kidney is one of the most prominently affected. Physicians who treat elderly patients must be aware of the decline in renal function that accompanies the aging process. The findings of urinary abnormalities or a decreased glomerular filtration rate (GFR) in elderly patients should alert clinicians to fully evaluate the renal function. GFR decreases steadily, starting in the middle age. Evaluation of elderly patients should include careful consideration of possible fluid and electrolyte disturbances. Acute renal failure is most frequent among the aged, mainly due to the comorbidities and the intervention they require. Diabetes and renovascular diseases including hypertension now account for most of the cases ofchronic kidney disease. The elderly are the fastest growing population of patients requiring renal replacement therapy in this aging society. This represents one of the great public health issues.