The hunt for a good biomarker for acute kidney injury (AKI) is currently hot. It has recently been the subject of several excellent reviews(1, 2 and 3) and a useful meta-analysis,(4) and we are hearing exhortations that this hunt should get high priority.(3, 5) The ideal marker (or set of markers) should facilitate early identification, stratify risk, and contribute to informative diagnostic classification. Perhaps most importantly, a good marker should aid the testing of interventions to prevent development of AKI and improve management. So, there are very good reasons to get on with it!