The development of a multilayer neural network may be divided into several steps: (1) problem formulation--determination of the task, which has to be solved (classification-prediction-data compression-diagnostics); (2) determination of the network topology (a larger than needed network may be designed and trained); (3) specification of learning patterns and relevant markers (sufficient number of patterns with known results and acceptable distribution among all classes, in which we want to classify); (4) determination of synaptic weights and other parameters of neurons (the problem of global optimization has to be solved, although no conditions for the existence of a solution are usually known); (5) evaluation of the generalization ability and (6) modifications by pruning the previously designed neural network.The utilization of neural networks has the following advantages: no knowledge of the exact algorithms for solution is necessary; very fast operation in the phase of utilization; possibility of future adaptation, when it is necessary: it also has the following disadvantages; huge time consumption during the phase of learning; difficulties in the determination of topology; difficulties in the creation of the training set, which must represent all possible classes; possibility of false results, with only limited tools for the recognition of this fact.Some examples of Neural Networks Utilization in medicine: General or specialised diagnostics (classification) myocardial infarction, coronary artery disease, PET scans of Alzheimer's disease. Evaluation of time-series (Signal Processing) evaluation of ST-T segments in ECG, evaluation of alpha and beta activity in EEG. Prediction of time-series, prediction of survival time, optimization of operation time, optimization of drug consumption. Decision support system for the decision if a drug may be used, for optimal determination of the time and type of drugs, for the optimal therapy choice. Picture processing, discovery of abnormal cells according to the recognized attributes, e.g. geometrical measures, discovery of tumours on the basis of different graphical transformations of X-ray pictures, etc.