Computer based information Systems aim at improving knowledge, évaluation and management processes. Such tools are still developing in the non- profit sector. This paper aims at : a) reminding how to evolve from data to management information Systems b) describing how to build a population based health information System c) describing the concepts required for conceiving a retrieval System and a system for inserting data d) documenting the importance of conceiving the system not only from a user driven perspective, but also taking into account the requirements of an information management System.