The relevance of action research to organisational change within contemporary health services in the United Kingdom is discussed in this article. Two examples of collaborative community-based studies are presented: one exploring ways to encourage community participation within a health and regeneration programme and the other considering the types of knowledge used within a "community of practice" to develop services for older people. The studies highlight the value of action research in bringing together citizens and health professionals to reflect on practice and to explore ways of improving service delivery. The article concludes that such "time-out" is important in supporting staff to internalise and shape processes of change. Furthermore, the forum which action research provides to bring staff and citizens together to plan, reflect on and evaluate their actions helps not only to develop services but also to challenge some of the traditional organisational processes which have excluded users and citizens. (Contains 3 notes and 1 figure.)