The paper presents the case of developing, adapting, and implementing an electronic prehospital patient records system in Scandinavia. The system is now fully implemented and it is used by all stakeholders within the prehospital domain. The paper focuses on the participatory design process of adapting the technical solution specified in the call for tender with the complex organizational context of actors with very diverse tasks and objectives and situated in five different regions each with their special geographical and demographical challenges. The paper concludes by discussing a range of lessons learned when using PD within a commercial project (where the starting point is a fixed contract and requirements specification), with a very diverse set of stakeholders (users, customers, and indirect users), and in a very complex domain encompassing a range of highly specialized competencies.