Argatroban was synthesized as a selective thrombin inhibitor in 1978. It was given approval to 10 mg/20 mL ampoules at first, afterward miniaturized dosage forms argatroban high-concentration ampoules (argatroban HI inj.: Slonnon HI inj. 10 mg/2 mL; Daiichi Pharmaceutical Co., LTD., Novastan HI inj. 10 mg/2 mL; Mitsubishi Pharma Corporation) were developed and soled in 2005. Argatroban HI inj. has concentrate glycerin 900 mg in an ampul as solvent that is known to affect a hemolysis. So when argatroban HI inj. is given to patients' blood vessel directly, it has need of dilution by some transfusion, but in case of giving it to a dialyzer in patients with hemodialysis, it is not always necessarily to dilute We investigated optical absorbance in collected blood-supernatant to see hemolytic affect of undiluted argatroban HI inj. in case of giving it to a dialyzer in beagle-dogs with hemodialysis compared with neg. control physiol. saline solution and reference control distilled water for injection. It did not recognize significantly increase optical absorbance in collected blood-supernatant compared argatroban group with physiol. saline solution group within 60 min after giving these materials. Distilled water for injection group increased the absorbance significantly at 30 and 60 min. After administration in comparison with physiol. saline solution group.