Fasciola hepatica, the most important trematode of domestic ruminants, is the most common cause of liver fluke disease in temperate areas of the world. In the USA, it is endemic along the Gulf Coast, the West Coast, the Rocky Mountain region, and other areas. It is present in eastern Canada, British Columbia, and South America and is of particular economic importance in the British Isles, western and eastern Europe, Australia, and New Zealand. Fasciola gigantica is economically important in Africa and Asia and is also found in Hawaii. Fascioloides magna has been reported in at least 21 states (USA) and in Europe. In North America, Dicrocoelium dendriticum is confined mainly to New York, New Jersey, Massachusetts, and the Atlantic provinces of Canada. It is also widespread in some areas in Europe and Asia. Eurytrema spp, the pancreatic flukes, parasitize sheep, pigs, and cattle in Brazil and parts of Asia. Several species of paramphistomes or rumen flukes are found throughout much of the world.