A magnetic resonance (MR) image detabase system has been developed. The purpose of this paper is to present this system and its application. It consists of an image processing system and database system to handle data of clinical cases and a medical knowledge base. Using the image processing system and the database system with stored data of clinical cases, the MR image data of cases can be retrieved by diagnosis as well as ID number, patient's name, etc., and MR images can be processed. By using the database system with the medical knowledge base, differential diagnoses can be offered.