This article describes the experience of developing an interactive Health Information System (iHIS) currently under test in a hospital, which benefited from the practices of the User-Centred Design (UCD), in a Participatory Design (PD) approach. Techniques from the Human-Computer Interaction (HCI) and/or Usability Engineering (UE), combined with traditional Software Engineering (SE), allowed an effective and usable solution from the user's point of view. The good results usually achieved with this approach were confirmed. Despite these good results, we deem that if there is not some control of the procedure by the project manager, it may be difficult to end the requirement analysis, since requirement reformulation is fostered.