Proper anticoagulation is an important factor in the function and life of the filter in CAVH or CAVHD and is the Achilles heel for CRRT. Several options now exist for anticoagulation and can be selected based on individual patient characteristics, availability of various anticoagulants, and local expertise. The choice of anticoagulant should be based on multiple factors, including A) the access site and whether an external pump is being used; B) the nature and geometry of the membrane; C) whether enhancements for ultrafiltration, such as predilution, are used; and D) the clinical status of the patient and preexisting coagulation abnormalities. Since anticoagulation in continuous therapy lasts longer than in intermittent hemodialysis, careful selection and monitoring are essential to prevent complications.