Our Medical Expert System has in its knowledge base twenty seven kidney diseases from nine different categories. The user is asked to answer with Yes or No if a certain symptom appears or not. In the end, based on the user's answers, the name of the disease is posted up on the screen. A drawback of this Expert System (and usually of any other) is that only the symptoms put in the knowledge base by the programmer are available. It does not think and does not learn by itself; however, the knowledge base can be updated anytime with new symptoms and new diseases.