The need for compliance to just in time (JIT) systems and other forms of production organization has caused many companies to make important changes in their structure, among them the analysis of the supply chain. Within this context, the procurement or purchasing begins to take on a principal role in the leverage of a company´s profit. On the average, companies spend 50% of their income from sales on the purchases of raw materials, components and suppliers. Due to this, the purchasing function is seen as part of a company´s logistics process, that is, as a part of the supply chain. The importance of the above has brought about the Strategic sourcing model which has undergone a profound study of products and supply market categories, resulting - besides an improvement in the processes, with the rationalization of consumption - in new specifications which increase the standardization of items of the same product for diverse units of a business. Initially, the purchasing function as its insertion in the supply chain will be analysed and the theoretical formulation of the Strategic Sourcing model will be presented. Later on the implementation stages of the PETROBRAS model and the results obtained will be described. Finally, the validation of the results will be carried out in the following dimensions: cost reduction in the supply chain, improvement in the level of service, supply discontinuation reduction and materials and products prioritization. This validation attempts to verify the adherence of the model applied to the assumptiores established by PETROBRAS.