Pathological changes of liver in infection of Fasciola hepatica. Fasciolosis caused by Fasciola hepatica is a hepatic parasitic infection that affects numerous mammal species, mainly ruminants, in several countries of Europe, Asia and America. The economic significance of fasciolosis is mainly due to direct losses caused by a decrease of weight rate, milking capacity and the confiscation of altered livers in slaughterhouse. In this review we present mechanisms of damaging of host liver during invasion of Fasciola hepatica. Parasites digest hepatic tissue and cause extensive parenchymal destruction with intensive haemorrhagic lesions and immunological reactions. Mechanical liver damage is due to migrating juvenile fluke. Macerated hepatic cells have been observed inside the oral sucker and pharynx. Moreover, the process of ulceration of liver tissue was observed in regions adjacent to the spiny body of fluke tegument. On the other hand, the injury of the liver can be induced chemically by factors produced or induced by the fluke. Probably, fluke proteases and other tissue-degrading enzymes can be responsible for negative effect on liver parenchyma. There is no evidence to link fluke-enzymes with tissue penetration. The consequences of liver damage resulting from the migrating flukes compromises liver function which is reflected in changes of plasma protein concentration (albumin, globulin). Additianally, changes of levels of hepatic enzymes released into the blood as a result of damage of liver tissue are used to monitor the progress of the infection in a variety of Fasciola hepatica hosts and as a sensitive diagnostic aid in field infection.