Opisthorchosis is a helminthiasis affecting mainly the hepatobiliary system and pancreas; its most dramatic complication is malignization of the organs infected by the parasites. The causative agents of opisthorchosis are two species of liver flukes, the trematodes belonging to the family Opisthorchiidae--Opisthorchis felineus and O. viverrini. The Chinese liver fluke, Clonorchis sinensis, also member of the family Opisthorchiidae, causes clonorchosis, a disease very close in symptomatology. According to different estimations, up to 40 million people are currently infected with these liver flukes and up to 600-750 million people in Eurasian countries constitute the risk group. These parasites colonize ever-increasing new areas in Eurasia where this disease has never been previously reported. Opisthorchiases are gradually transforming from a local problem of individual geographic regions to a widespead problem; in particular, O. viverrini is now referred to as "an underestimated parasite." As we see it, O. felineus has all the reasons to share this status. First and foremost, the observed expansion is likely to be connected with the ever-increasing intensity of traffic flows and migration of the infection carriers between cities, regions, and countries. This review briefs the characteristics of O. felineus and the other liver flukes persisting in various countries of Eurasia, clinical manifestations of opisthorchosis, the drugs for chemotherapy of trematodiasis, and the strategy for discovery of new antihelminthic drugs.