West Nile fever is a mosquito-borne virus involving wild birds as amplifying hosts, and humans and horses as highly susceptible and incidental hosts. Outbreaks of West Nile fever have already been reported in metropolitan France, in the Camargue region between 1962 and 1965. After 35 years without any evidence of viral transmission, West Nile fever is reported again during 2000 in horses from the Camargue region. Following this outbreak, passive surveillance of equine encephalomyelitis has been reinforced in French departments, particularly in those bordering the Mediterranean. This surveillance led to the identification of four distinct outbreaks of West Nile fever, responsible for neurological illnesses in horses of Camargue region between 2000 and 2004, while 2003 and 2006 in the Var department and eastern Pyrenees, respectively. The equine surveillance system allowed sensitive detection of hot-spots of viral amplification in the regions, and could be reinforced by a syndromic surveillance protocol to facilitate earlier detection. The situation in the French West Indies is in many respects different from that in metropolitan France, but the need for West Nile virus surveillance has been underscored by the rapid spread and increased virulence of the virus that was introduced onto the American continent. In this context, an active surveillance system based on regular serological controls of the equine population was useful in demonstrating active viral transmission in Guadeloupe between 2002 and 2003, without any recorded human or equine clinical cases. Results obtained by surveillance in metropolitan France, Guadeloupe and Martinique between 2000 and 2007 are presented.