The current goal of our research is to build a Japanese medical ontology. It becomes a key to the successful development of various knowledge processing applications for systematization of vast medical knowledge and the synthetic understanding of them. This article discusses a fundamental consideration of medical ontology based on ontological theory. We focus on "anatomical structure of organs" and "abnormal state in the human body". On the basis of the investigation, we distinguish organ-specific concepts from those independent of any organ. And we described abnormal states of a human body by the same framework which is represented by an object, its attribute and its value(abnormal type). These discussions give a guideline to fill the gap between different medical domains through establishment of common concepts across various branches of medicine.
