Participatory Design (PD) methods in the field of health informatics have mainly been applied to the development of small-scale systems with homogeneous user groups in local settings.Meanwhile,health service organizations are becoming increasingly large and complex in character,making it necessary to extend the scope of the systems that are used for managing data,information and knowledge.This study reports participatory action research on the development of a PD framework for large-scale system design.The research was conducted in a public health informatics project aimed at developing a system for 175,000 users.A renewed PD framework was developed in response to six major limitations experienced to be associated with the existing methods.The resulting framework preserves the theoretical grounding,but extends the toolbox to suit applications in networked health service organizations.Future research should involve evaluations of the framework in other health service settings where comprehensive HISs are developed. 2007 Elsevier Inc.All rights reserved.