The article contains a review of main features of intellectual data analysis, its methods with the examples of possible mathematical realisation and tasks. The article also contains examples of realisation of intellectual data analysis in the tasks of medicine diagnosis. The main principles and stages of construction of hierarchical model for determination of causal relationships in the database are expounded in the article and the necessity of usage of this model for data organisation in database is given. The basis of building neural network for medical tasks is given as well as an example of real realisation of a neural network.