Acute kidney injury (AKI) is common in ICU patients and is associated with increased mortality. Attempts to develop therapies to prevent or attenuate AKI have had no demonstrable success. One major reason for this failure may be a consequence of our inability to detect AKI early enough. Thus, finding reliable, early biomarkers of AKI is an important research goal. Innovative technologies such as functional genomics and proteomics have facilitated detection of several promising early biomarkers of AKI such as neutrophil gelatinase-associated lipocalin (NGAL), cystatin C (CyC), liver-type fatty acid binding protein (L-FABP), hepcidin, glutathione-Stransferase (GST) p and a, and kidney injury molecule-1 (KIM-1). These biomarkers have many potential applications and are challenging creatininea??s supremacy in the clinical arena as the dominant biomarker. They can be used to evaluate the effect of new techniques and therapies on kidney function, as safety markers to monitor toxicity and as measures of treatment effect. This issue of Current Opinion provides an important update on new developments in this field.