21st century is considered as century of Information Technology. During current era information technology is involved in all areas of our life. One of the applications of information technology is to develop expert system which is applications that are trained to work like human which contains all human expert knowledge. There are several major application areas of expert system such as agriculture, education, environment, law, manufacturing, medicine, power systems etc. The idea of expert systems has also been widely accepted in Medicine environment, starting from a simple database query to complex treatment recommendation.Expert systems can be applied in various tasks of medicine domains such as Generating alerts and reminders, Diagnostic assistance, Therapy planning, Image recognition and interpretation. This book will provide knowledge regarding development of knowlegebase system for diagnosis and prescription of medicines