The innovations of Computer Sciences have revolutionized the human life. As a result the ability to simulate activities and processes has grown significantly in recent years. It has made easy to analyze and diagnose the medical problems and diseases.The use of Artificial Intelligence in medicine and medical sciences is on high demand. Different methodologies are used for the implementation of Decision Support Systems that can help Medical Professionals for identification and diagnoses of diseases .Each methodology has some good aspects as well as some dark. The selection of a particular methodology depends upon various parameters of problem domain. Certain methodologies are more effective within one domain while other may be in another. A detailed study of most commonly used methodologies in Health Care can help us to suggest an optimal methodology for clinical decision support systems.