A kypsin inhibitor was isolated and purified from Mung bean (Vigna radiata L. wilczek) which has been used as a galenic and traditional food. In addition, we evaluated the pharmacological effect of the mung bean trypsin inhibitor (MBTI) using septic shock induced guinea pig model. Purification was carried out by Sephadex G-50 gel filtration, DEAE-cellulose ion exchange chromatography, and trypsin affinity column. The molecular weight of MBTI was estimated to be about 8,000 Da by 20% SDS-PACE under reducing condition. The chemically determined partial amino acid sequences of the purified MBTI perfectly coincide with those of previously reported MBTI which is BBI type trypsin inhibito. (Bowman-birk inhibitor type). These results suggest that the purified MBTI is authentic. Hypotension shock was prevented by the pretreatment of the MBTI (10 mg/kg of the body weight) on the septic shock guinea pig model caused by psedomonal elastase.