Given the devastating effect that acute kidney dysfunction (AKD) has on the clinical course and outcome of critically ill patients, it is incumbent on every intensive care provider to understand the causes and effects of AKD. AKD is common and costly and even mild forms warrant attention. Promising new therapies are being explored. But even after they arrive, attention to first principles of avoiding further injury from volume depletion, hypotension and nephrotoxins will be of the primary concern of Intensive Care Unit (ICU) team. For established AKD, more and possibly sooner renal replacement therapy is likely to be better than less and later.