To investigate the effects of trypsin inhibitors, aprotinin and urinary trypsin inhibitor (UTI), on the cute pancreatitis, this study was carried out in dogs of acute pancreatitis induced by oleic acid (0.28 mg/kg). Administration with aprotinin and UTI seemed to have a therapeutic effect on the clinical sign, ultrasonographic finding, histopathologic finding. But in amylase and lipase activity, there were no significant differences among three groups.