The book describes numerous results obtained by Soviet and foreign authors when studying various aspects of the theory of training in pattern recognition. Along with setting the training task, methods for solving it are described in detail. Particular attention is paid to research, convergence of recurrent learning, self-learning and adaptation procedures. The work reflected the main approaches to the task of training. The book is designed for scientists engaged in the field of theoretical and technical cybernetics. In addition, it can serve as a textbook for undergraduate and graduate students specializing in the theory of trainable and adaptive systems.