Continuous renal replacement therapies have advantages over intermittent hemodialysis in the treatment of critically ill patients with acute renal failure. Dialytic regimens which have therapeutic aims in common with other continuous renal replacement therapies have been developed; these include lower solute clearances that are maintained for longer periods of time. For reasons of cost, simplicity, and convenience, attempts have been made to adapt intermittent hemodialysis machinery for continuous renal replacement therapy. Sustained low efficiency dialysis using the Fresenius 2008H/4008K series or Genius machines is safe, convenient, and provides excellent control of electrolytes, with good tolerance to ultrafiltration. Hemodialyzer clotting is a common complication.