This work evaluated the effective and potential importance of biodiesel for soybean production in Brazil and its regions in 2008, as well as if the prices of biodiesel had been adjusted according to the interests of producers and consumers. Four situations were considered: the first one refers to the application of Law 11.097/05, which resulted in a production of 1.164,33 million liters of biodiesel (912,83million liters of soybean biodiesel), which corresponds to 2,6% of the national diesel consumption in 2008. Alternatively, an estimate was made of what would happen if the percentage of the mixture had been 4%, 5% or 8,3%. In 2008, it is estimated that 8,5 % of the soybean produced in Brazil was directed for biodiesel production, and this percentage would increase to 13%, 16,3% and 26,9%, in the case of the other mixtures. Considering the production cost estimates of the soybean and biodiesel of the 2004/05 crop and comparing them with 2008, it was observed that the prices obtained by the soybean and biodiesel producers were attractive, regarding both the production costs and the price of the soybean. For the consumer, it was estimated that the 2,6% biodiesel mixture increased diesel prices in 1,45% in 2008. The other mixtures lead to prices increases of 2,15%, 2,69% and 4,46%.