There is a paucity of high-quality evidence to guide clinicians on thresholds for commencement of renal replacement therapy (RRT) in critically ill patients with acute kidney injury (AKI), and wide international practice variation. Wald et al. report a pilot randomized trial examining accelerated use of RRT for moderate AKI in the intensive care unit, providing a workable design for a definitive trial examining the timing of RRT in critical illness.