A number of application systems for medical information services were developed. However, each of those application systems was developed independently out of consideration for other applications. Therefore, there are many problems in operation of the systems. Users(hospitals) have to prepare communication lines and equipments for using each service redundantly, and facilities for operation of those systems are also furnished individually. Thus, it is necessary to integrate the medical information systems in standardized environment in order to reduce operating costs and upgrade the services. This paper analyzes the methodology for development of an integrated medical information system in common environment and summarizes the result of the integration and standardization. Finally, we studies the directions for expanding the integrated system and activating the services.