-The sharing of medical information among healthcare providers is a key factor in improving any health care system. By providing opportunities for sharing and exchanging information and knowledge, data center, agent and ontology play a very important role in the field of medical informatics. In this paper, we propose a design of architecture and data center for the development of a Hospital information system (HIS) based on agents and ontology. Health networks in general, are supported by IS. These IS are structured particularly around medical record to support the storage, access, dissemination and sharing of patient information [1] .To be more effective and to make the right decisions at the right time, Hospital information systems (HIS) needto have high quality of information: relevant, reliable, accurate and actual. In addition, this information must be stored, updated and made available to the different actors involved in the care system whenever is necessary. For care providers, information is a strategic resource that is essential to be mastered because it contributes to the quality of decision. It is the role of HIS to disseminate information, regardless its nature, to relevant stakeholders.The HIS is a typical collaborative information system in which people such as physicians, nurses, professors, researchers, health insurance personnel, etc. share patient information (including text, images, and multimedia data).It makes data available for the following uses: patient care, administrative and business management, monitoring and evaluating medical care services, epidemiological and clinical research, and planning of medical care resources [2] .