In the intensive care units of Japan, nafamostat mesilate (NM) is the most used anticoagulant of continuous blood purification, with the rate of up to 85%. Its biggest characteristic is not to reduce the life of the filter in the group of patients with high risk of bleeding, and it can be safely used. However, there are not a few reports about severe anaphylaxis, when the symptoms of anaphylaxis is recognized after the start of continuous renal replacement therapy, it should be kept in mind that it is NM hypersensitivity. In addition, for an expensive drug, it may be required to be limited in the cases of risk of bleeding complications. NM has been developed for nearly 30 years, so it has high reliability in Japan. However, in the same case, regional citrate anticoagulation is recommended internationally. It may need a randomized controlled trial with regional citrate anticoagulation to prove the real effectiveness of NM.