Ephemeral fever is a viral disease of cattle and water buffalo. The more spectacular epidemics of the disease have occurred in subtropical and temperate regions of Africa, Asia and Australia. However, the virus has its home essentially in the tropics. The clinical effects and epidemiology of the disease have been better studied in the fringe regions than in its heartland. Without a much deeper study of the ecology of ephemeral fever in the tropics the benefits of control measures cannot be demonstrated for the endemic regions.