From a situation of little importance in French crops (324,000 hectares in 2004 including 300,000 hectares of rapeseed), the surface area of energy crops should quickly grow in order to increase the level of incorporation of biofuels in fossil fuels to 5.75% by 2010 (recommended value of Directive 2003/30/EC, “promotion of biofuels”). The French government recently increased the authorized quantities of biofuel production. In the present context where oil prices are close to 70$ a barrel and where the fight against global warming has become a priority, biofuels are shown in quite a favourable light. However, considering, on the whole, their very poor energy yield per hectare of land and their high costs, we are led to temper the very optimistic analyses carried out on them. Essentially presented as energy chains, it should not be forgotten that biofuels are also an indirect way of supporting agribusiness and agriculture, under the responsibility of each country. The main results summarised here concern France. They are obtained by using a dynamic and partial equilibrium model, OSCAR (Optimisation of the Economic Surplus of Renewable Agricultural Biofuels), developed by the INRA (France) (frame 1). The strong points of this model consist in a detailed formalization of food and non-food agricultural supplies, considering CAP evolutions and the impacts of biofuels on farming incomes as well as on farming jobs.