Principles and requirements of Action Research - The paper is focused on the principal aspects of action-research and on the principles that make possible the virtuous circle between research and action. The author explores three aspects: the link between action and research, the researchers-local stakeholder relationship, the outcome of the research process. The virtuous circle between research and action is promoted by the reflective practice and the possibility to co-construct shared representations among researchers and local stakeholder. Keywords: reflexivity, participation, inter-subjectivity, action research