Caustic sclerosing cholangitis occurs with the use of scolicidal solutions in liver hydatid disease draining into the biliary system. In this study, we investigated the effectiveness of benzimidazole solutions, their in vitro scolicidal effects and the histopathological changes in the hepatobiliary system due to their intraoperative use. It was found that 5 mg% mebendazole and 1 mg% albendazole have strong scolicidal effects. In an in vivo study, under general anesthesia, 5% mebendazole in group I, 1% albendazole in group II and normal saline in group III were injected into the biliary system of rabbits. Liver biochemical tests showed no significant changes. More elaborate ductal mucosal proliferation, ductal dilatation and periductal fibrosis were found in group I compared with group II in biopsies taken on the 60th day. The biopsies of group III were normal.