Acute renal failure (ARF) is frequent in aged individuals. In this article, we review the literature and relate our own experience in this field. It is concluded that there are no technical reasons to deny treatment for ARF using any of the available techniques based on age. Attempts to prevent the onset of ARF are important. Prophylaxis may be focused on diligent and adequate diagnosis and treatment of reversible renal hypoperfusion, by far the most common cause of pre-renal ARF in the elderly. Administration of potentially nephrotoxic drugs should be avoided, but when necessary creatinine clearance (as the marker of glomerular filtration) rather than blood creatinine levels should be used to establish the appropriate dose. In the elderly, azotemia or other consequences of ARF may induce acute behavioral changes that are almost always reversible; treatment should not be stopped on the false assumption that the patient's mental status is irreversible.