There is a worldwide consensus for using the diagnosis related groups (DRG) when considering hospital activity. This tool leads to the production of tables of numbers (case mix), the interpretation of which is difficult. Therefore, methods aimed at facilitating this interpretation are needed. One of such methods is the case view, i.e. a graphical representation of the case mix. It reduces, in a way, each DRG to a "pixel", the set of the DRGs being an image (the case view). The reference set should be organized according to three criteria: medical/surgical, nosological and economic. This method can be used to answer theoretical questions or to visualize activity at the level of a hospital or at the level of a department. The purpose of this paper is to present important principles inherent in this graphic representation, both at the level of the method and at the level of the user.