In France, horse rearing is often associated with other farming activities such as beef or dairy productions which prevail in grassland areas. To analyze the impact of horses in the sustainability of farming systems, we surveyed a hundred farms in four major areas of horse breeding, which are chosen according to their productions system representative of regional agricultural systems. Regions differ by their agro-climatic context associated with a type of horse production: saddle horses in oceanic and continental plains and draught horses in two mountainous regions in Central and Eastern France. Farmers have been questioned about the role of the equine production in economic, environmental and social functioning of their farming system. Results showed the horse number varied from less than 10% to 100 % of the total livestock (expressed in Livestock Unit). In mountainous areas, draught horses were appreciated to use grasslands at the same time or after cattle. These hardy horses needed a little labour but the low income of this production limited its development. In plains, farmers raised saddle horses either alone or with dairy or beef cattle. In farms specialized in horses, breeders developed services linked to horses as taking horses at livery. In mixed herds, farmers spent comparatively more time for horses than for cattle, whatever the type of beef or dairy productions. The saddle horse impact on gross production depended on the equine number and on the age for sale. In conclusion, horse rearing could present a low profitability especially for draught horses or an unpredictable one especially for saddle horses. But, whatever the types of animal productions, the horse grazing improved the maintenance of grassland areas and farmers raised horses because they liked to take care of these animals which attracted volunteer labour.