Dextran 40, a polysaccharide with molecular weight of 40,000, has been used clinically for expansion of plasma volume, improvement of microcirculation in low flow states and thromboprophylaxis especially in major operation such as vascular and hip surgery. However severe anaphylactoid reaction to dextran 40 can occur rarely. We experienced a case of cardisc arrest due to a severe reaction of dextran 40 in a patient who underwent aortofemoral bypass surgery. The patient was resuscitated immediately and followed up carefully.