ABSTRACT: We summarize original research in the field of critical care nephrology accepted or published during 2008 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Three main topics have been identified for a rapid overview. (1) The classification of acute kidney injury, with particular attention to differences and similarities between the RIFLE and AKIN classifications. (2) Fluid balance in patients requiring renal replacement therapy (RRT) has been shown as an independent risk factor for mortality in critically ill patients: current evidence and uncertainties are described. (3) Management of anticoagulation during RRT has been explored by several researchers in 2008: diagnosis of heparin-induced thrombocytopenia, the use of tirofiban and optimal anticoagulation during drotrecogin A activated treatment have been evaluated.