Rafal Latkowski Hopfield Neural Networks --- Theory and applications (in Polish) Bachelor thesis under supervision of Professor Andrzej Skowron. Warsaw University, Institute of Mathematics, 1999 39 pages Abstract This Bachelor Thesis describes the functioning and construction of Hopfield Neural Network based on simple application (TELE-TEXT Noise Removal). In the first chapter the short historical introduction is provided together with placement of Hopfield Neural Networks in history of research on Neural Networks. The second chapter presents the idea of Hopfield Neural Network and probabilistic proof on the network capacity estimation. The third chapter presents an application of the HNN's to the TELE-TEXT Noise Removal problem. Based on the experimental evaluation the theorem on reduced network capacity and stability condition is formulated. Main Result The main result of this work is a theorem with proof, that even in spite of the well known estimation of the maximal Hopfield Neural Network capacity (c=0.138*N), there always exits many triples of patterns, which cannot be learned by the neural network. The proof is constructive, i.e. it constructs the finite family of counter-examples.