Data mining a promising field of research in which many researchers are working. It may be viewed as extraction of patterns and models from observed data. The area of data mining is very broad as it incorporates techniques and approaches from different research disciplines. Data Mining is usually used to answer two types of application questions; generate predictions on the basis of available data or describes the behavior captured in the data. Today medical data sets have enormous capacities. These data may contain valuable information that awaits extraction. The knowledge may be encapsulated in various patterns and regularities that may be hidden in the data. Such knowledge is priceless in decision making.