This article describes how research-based knowledge was used in practice in an action research project which examined student dropout. The research was conducted as 'research circles' and involved systematic and organised cooperation between researchers and practitioners, in this case college teachers. Based on interviews with the teachers, we found that research-based knowledge was used in a variety of ways: as concepts for discussing real-world experiences, as confirmation of the teachers' practical experiences, as a frame for understanding praxis, to inform action, to conduct research activities, and as a way of legitimising the importance of the practitioners' performance in their daily work. The teachers used knowledge from previous research as well as that developed during the course of the project. However, findings indicated that research-based knowledge appeared to be more useful for talking about and understanding practice rather than guiding practical action. In order to deepen its impact on practitioners' actions, researchers and practitioners should work together to translate research-based knowledge and theoretical concepts into practice and specify how practitioners can apply it when developing their actions. Therefore, action researchers should allocate time to the process of transforming research-based knowledge into practical actions -- in co-operation with practitioners -- as an integral part of their research project.