Application areas such as Statistics in fields such as information retrieval, speech processing, bio information, and communications often involve either small scale or large scale models in which thousands of random variables are linked in complex ways. Also on probabilistic models, they are used in probability theory. In this project we review some of the basic ideas underlining graphical models, we present coding in R under the graphical model, look at Bayesian networks and the probabilistic relationships between diseases and symptoms and some software packages presented.