The first detailed account of bovine ephemeral fever (BEF) appeared in the French literature. All the essential clinical features of an epizootic of ephemeral fever in cattle were described as “dengue of cattle” in lower Egypt in 1895. The causative agent, BEF virus, was first transmitted successfully from cow to cow by Bevan and the infection was characterized in comprehensive studies using cow inoculation as the assay system. BEF virus was not isolated in another host until 1966 in South Africa. The known vertebrate hosts of BEF group viruses are all cloven-hoofed herbivores. They include cattle, water buffaloes, Cape buffaloes, deer of at least two species in Australia, and herbivores of various African game species. Antigenic differences do occur between BEF strains isolated from cattle with clinical disease in different epizootics by in vitro comparisons as judged by cross-N tests using mouse ascitic fluids.