Although acute renal failure (ARF) requiring dialysis affects only approximately 4% to 7% of patients admitted to the ICU, such individuals tend to be the sickest and most challenging patients in the ICU. The presence of ARF dramatically complicates their care and mandates the use of extracorporeal renal replacement therapy (RRT). The use of such therapy, with its technical and physiological demands, further complicates treatment. Not surprisingly, therefore, several controversies surround the management of these patients: the techniques of RRT, the indications and timing for their application, the intensity of their use, the selection of suitable patients, the nature of appropriate monitoring and physiologic targets for their application, the type of specialist best suited for the daily management of such patients, the cost-effectiveness of RRT, and the expansion of its use to treat patients without ARF. In many ways, the response to these controversies has diverged between Europe, Australia, and New Zealand on the one hand, and the United States on the other. In this article, we illustrate these sometimes quite different philosophies by presenting two perspectives (from Australia and the United States) on a number of important issues pertaining to RRT.