In this study, using PC server. we developed large scale hospital order communication system which is classified into 3 categories of business: clinical business, clinical support business, patient management business. In all the programs to build OCS, the user's convenience was considered as a top priority. which was built in the environment of 'window'; in this, the tool to develop the programs was a 'Visual Basic' In consideration of the aspect of operation. the programs were consolidated into one kind. The database was built into a relation-type database. MS/SQL which is easily interchangeable or portable personal database: and data exchange with real users was also made casy. Since all kinds of business concerned built in open system, this hospital information system can actively cope with any of environmental changes, and since this system was developed by manpower within an organization of a hospital. the system can flexibly and efficiently correspond to its operation.