The incidence of perioperative renal injury appears to be increasing in the ever more complex elderly population presenting for cardiac surgery. A subgroup of intensivists and critical care nephrologists has formed the Acute Kidney Injury (AKI) Outcomes and Quality Study Group. This group has agreed upon a new definition of acute renal injury, which replaces "acute renal failure" and enhances the recent Risk, Injury, Failure, Loss, End stage (RIFLE) criteria. The risks for bleeding, wound complications and nutritional compromise are also increased among patients with AKI. The most important patient-related issue predicting AKI is pre-existing chronic kidney disease. General measures that have been proven to prevent AKI include adequate preoperative hydration, avoidance of nephrotoxins and optimization of hemodynamic parameters. Natriuretic peptides are also theoretically attractive as agents for the prevention of AKI. Finally, prophylactic dialysis has been proposed for patients with pre-existing advanced kidney disease.