This book covers a wide range of issues related in one way or another to the presence of any disorder in the atomic or electronic system of condensed matter - from the statistical theory of liquids and the theory of phase transitions to the physics of polymers and electronic processes in liquid metals and highly doped semiconductors. Various types of disorder have been studied (topological, substitution disorder, etc.). The book can be recommended to senior students of physics departments, as well as graduate students - experimenters and theorists, teachers, scientists interested in condensed matter physics.