A medical information system has a terminal device of a hospital information system for retrieving and displaying an examination list and a reading report and an image display terminal device for displaying an image. Both terminal devices are arranged to mutually transfer the identification information of an examination to enable their displayed contents to be changed interlockingly. Therefore, medical information, such as charts, medical images, reading reports and results of examinations, required to perform a diagnosis is formed into electronic data and electronic data is displayed on a screen to provide information for a doctor.