Since its birth in 1978, DIOGENE, the hospital information system of Geneva University Hospital has been constantly evolving. with a major change in 1995, when migrating from a centralized to an open distributed architecture. For a few years. the hospital had to face health policy revolution with both economical constraints and opening of the healthcare network. The hospital information system DIOGENE plays a significant role by integrating four axes of knowledge: medico-economical context for better understanding and influencing resources consumption; the whole set of patient reports and documents (reports. encoded summaries, clinical findings, images, lab data, etc.), patient-dependent knowledge. in a vision integrating time and space: external knowledge bases such as Medline: (patient-independent knowledge); integration of these: patient-dependent and independent knowledge in a case-based reasoning for mat. providing on the physician desktop all relevant information for helping. him to take the most appropriate adequate decision. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.