This dissertation begins with a discussion about the importance of inventory control to companies with a special approach for inventory control of spare parts. It shows that an efficient control of this kind of inventories can avoid large financial losses, due the high stock carrying and stock-out costs. Besides the economic perspective, the inventory of spare parts can have important strategic functions. Next, the text presents the recent development of spare parts´ inventory control. Then it is proposed a model based on the (r, q) control system, in which the optimal stock level is achieved by a service level restriction. Finally, the model is used to estimate optimal stock levels of some Landulpho Alves-Mataripe Refinery´s spare parts.