A serological survey of Rift Valley fever was carried out in sheep in Côte-d'Ivoire. Thousand and fifty one seras collected between 1988 and 1990 in the South of the country were tested for IgG and IgM by ELISA with two objectives: determining the incidence of the Rift Valley fever and analysing the role of this virus in reproductive failure and abortion. The incidence rate was 6.85%. No difference was found between the three different geographic areas nor between the three years of the survey. Antibody prevalence increased significantly with age. The Rift Valley fever must be considered as enzootic in Côte-d'Ivoire. A significant relationship was found between positivity and abortion in ewes. Thus, the economic impact of Rift Valley fever has to be studied. The presence of antibodies in young animals aged from 6 months to 1 year, showed a recent activity of the virus; a permanent epidemio-surveillance of the Rift Valley fever in Côte-d'Ivoire is needed, because of the potential risk for human population in contact with the animals.