Technological development and increased international competition have imposed a significant burden on the product development function of many companies. The growing complexity of products demands a larger product development team with people having various competencies. Simultaneously the importance of good quality, usability and customisation of products is growing, and many companies want to involve customers and users directly in the development work. Both the complexity and quality demand new ways of working that support collaboration between people with various competencies, interests (...) and responsibilities both inside and outside the company. This paper reports experiences from using action research to introduce new user-centred work practices in two commercial product development projects. The interventions varied. In the first project it was found rewarding to engage customers and users in workshops based on participatory inquiry and collaborative design. The design process was iterative and the workshops took place several times involving concept through detailed design. In the second project, new design representations are introduced. The experiences highlight the importance of creating and reifying insights in design representations and using these to both support collaboration, and create continuity in the project. The paper ends with a discussion of scientific rigor in action research and what the new work practices imply for the development team. (shrink)