Liver flukes-induced pathological changes in liver parenchyma and biliary passages are so severe that, in some cases, may cause total physiologic dysfunction. The human disease is endemic to some parts of the country, and there were two vast epidemics of the human fascioliasis in Gilan province, northern most part of the country. According to WHO reports , the human disease is prevalent in Gilan, Mazandaran, and Isfahan. However , the aim of the present study was to collect more information about the naturally- infected animal hosts, and to extend the Knowledge to prognosticate the pathologic effects occurring in human cases of liver flukes in endemic parts of the human disease. The present study was carried out in slauther houses of Gilan and Khuzestan province, two most endemic areas of human and animal Distomatosis, respectively, from spring 2002 to summer 2003. A total of 30 infected livers were collected, and were examined both for visible gross and microscopic changes. The results of the present study showed that the pathologic changes varied from mild effects to total biliary bstruction. Most of the present knowledge on pathology of the human disease is based on studies in animal models. To have precise and comprehensive information about the tissue changes in naturally –infected animal may help to describe some unanswered concepts about the pathology of the human distomatosis.