Design activities are becoming more and more complex. This leads designers to work in highly collaborative and distributed teams. The Purpose of this study is to investigate on improving the use of KMS by defining a descriptive model of the knowledge transfer within engineering teams. We started by a literature review and we adopted a participant observation methodology in order to propose this model. Then we tested our model through case studies. This investigation enables us to observe, define and model more finely the dynamics of the exchanges between knowledge workers.