Increasing the dose of renal replacement therapy might increase survival in critically ill patients with acute renal failure. For continuous renal replacement therapy (CRRT), a single-center study suggests that increasing urea clearance from 20 ml/kg/h to 35-45 ml/kg/h might increase short-term survival. A further single-center study has now confirmed that the dose of CRRT might be a determinant of outcome. This issue is now being addressed by two large multicenter randomized controlled trials in the United States (the ATN study) and Australia and New Zealand (the RENAL study). The results of these two studies should be available in 2008. Before making any major changes to practice, it seems prudent to wait for the publication of the findings of these two pivotal trials.