We have constructed an object-oriented database system, using prescription, lab test result, and disease registry data, transmitted from the order entry system of Hamamatsu University Medical School Hospital. It serves not only numeric data but also semantics of laboratory results. The database system has a feature to categorize each data into structured hierarchies of attributes. By this, the user can retrieve abstract level descriptions such as "prescriptions of anti-inflammation medicines, suppository only", "any kind of gastric ulcer", etc., which is expected to be useful for researchers and students. In transferring order entry data from HIS, HL7-ASTM E1238 standard data formats using the Japan Association of Clinical Pathology lab test item code are utilized, proving this system's transferability to other hospitals. This is the first real use implementation of an object-oriented data base in a clinical setting, and results are promising in terms of providing an intelligent clinical database. Also discussed are future trends of clinical master files, hospital administrative tools, and multi vendor configurations of HIS.