Recent studies suggest that the enhanced release of reactive oxygen species (ROS) plays an important role in the pathogenesis of clinical acute pancreatitis. In the present study, we investigated the effects of the free radical scavenger edaravone, which is used clinically as an anti-stroke agent, in the development of experimental closed duodenal loop (CDL)-induced acute pancreatitis. In the CDL-pancreatitis model, after edaravone and vehicle saline were injected intravenously, pancreatitis was induced for 7 h by the CDL technique. The subsequent ascites volume, wet pancreatic weight, serum amylase levels, and pancreatic tissue lipid peroxide levels were evaluated. Pancreatic tissue damage was also evaluated histologically. In this CDL-induced pancreatitis model, edaravone treatment tended to reduce the ascites volume and inhibit the increases in the wet pancreatic weight. Edaravone also tended to reduced the microscopic mucosal damage scores and pancreatic tissue lipid peroxide levels. In particular, the serum amylase levels in the edaravone-treated rats (1-20 mg/kg i.v.) were significantly reduced as compared to the vehicle-treated rats. These results strongly support the involvement of ROS in the pathogenesis of CDL-induced acute pancreatitis and cytoprotective effects of free radical scavender against pancreatic acinar cells. A clinical effect for edaravone against acute pancreatitis is strongly expected.