Περιέχει το πλήρες κείμενο ; The Dutch curriculum for mechanics is being revised with a focus on educational approach rather than on content. By integrating effective designs from small-scale research projects and using cyclical feedback from teachers who implement the design, an effective balance is sought between educational innovation and practical effectiveness. Each cycle of the design process consists of phases of writing, implementation and evaluation. From 2006-2008, two complete cycles and a third writing phase have been completed. This study analyses how the designers construct and justify their design, primarily to themselves, through a negotiation of design ideas, educational objectives and pedagogical concerns. Participatory action research is used to reconstruct the process from internal and external communications. Design ideas are most actively produced and negotiated during the writing phases, so that differences between designers stand out prominently. These are interpreted as based in different ‘cultural orientations’ between educational and research backgrounds. What emerges is a still-evolving compromise rather than a consensus view. During and after classroom trials designers have to consider whether and how to accommodate the concerns of the teachers. The teachers too appear to have various and divergent concerns. For an important part, these differences can be understood as different ‘curriculum emphases’. This paper argues that concerns of different kinds of experts on the same design issues are likely to be difficult to reconcile, and presents provisional approaches to reconciliation that were constructed in this project. Our interpretation of teachers’ concerns is shown to guide the continuing revision of the design. Further research will be directed at establishing the stability of these solutions and determining effective professional development strategies for aligning designers’ and teachers’ concerns.