This book is a complete treatise on the theory of nonlinear dynamics of chaotic and stochastic systems. It contains both an exhaustive introduction to the subject as well as a detailed discussion of fundamental problems and research results in a field to which the authors have made important contributions themselves. Despite the unified presentation of the subject, care has been taken to present the material in largely self-contained chapters. The present book can thus be used either as a textbook by graduate students or as a modern monograph by researchers in this field. The second edition has been substantially enlarged to include sections on statistical properties of dynamical chaos, on effects of synchronization in oscillatory systems and on synchronization in living systems.