Acute renal failure (ARF) is commonly encountered in the intensive care unit. It is associated with considerable morbidity and mortality. There are many possible aetiologies in the critically ill, including nephrotoxic agents, hypovolaemia, and sepsis. Whilst many classification systems for ARF exist, the RIFLE (Risk, Injury, Failure, Loss, End-stage) criteria and the Acute Kidney Injury Network (AKIN) criteria are the most commonly utilized. Many supportive therapies are employed to minimize the degree of renal injury once recognized, such as fluid resuscitation, maintenance of an adequate mean arterial pressure (with the use of inotropes if persistent hypotension despite fluid and treatment of the underlying aetiology); however, if renal failure becomes established, then renal replacement therapy (RRT) may be needed to maintain homeostasis. A number of specific renal-protective agents have been studied (i.e. dopamine); however, to date none have demonstrated a clear benefit. While there are no clear guidelines with respect to the ideal mode or intensity of RRT we will discuss pros and cons of the various bedside options. ? 2012 Elsevier Ltd. All rights reserved.