Clinical evaluative research are far too few. In this article, the authors describe a research process likely to favor its multiplication. They report on a case study of a process resembling a cooperative action-research led by a group of clinicians in pedopsychiatry. With the results and in the light of caracteristics of action-research, they explain why and how this group of clinicians has succeeded in establishing a research process. The lessons drawned from this experience are numerous. The authors conclude by proposing a cooperative action-research as a model that all clinicians could apply to a clinical study.