:Building software models before implementing them has become widely accepted in the software industry. Object models, graphically represented by class diagrams, lay the foundation for all later design work. So, their quality can have a significant impact on the quality of the software which is ultimately implemented, and an even greater impact if we take into account the size and complexity of current software systems. It is widely recognised that the production of better software requires the improvement of early development phases and the artifacts they produce. In this paper, we will introduce and analyse a set of an existent object oriented metrics that can be applied for assessing class diagrams complexity at the initial phases of the object oriented development life cycle. We also define our own proposal for new ones. KEY WORDS: object oriented metrics, object oriented software quality, class diagram complexity RESUME: La construction de mod