The purpose of this book is to systematize the available material and to delineate the principal trends in the investigation of those closely interrelated properties—thermal (heat capacity, thermal conductivity, thermal expansion), acoustical, dielectric, visco- elastic, etc.—which govern the entire set of important physical properties of polymers at low temperatures. An attempt is made to show how the chemical constitution and the supermolecularstructure influence the physical properties of polymers in the low- temperature region·All the chapters of this book, except the last two, are organized according to the same plan. Each chapter, devoted to a single physical property, consists'"of three sections. First, the theory of the property under discussion and the related physical phenomena are briefly considered. This is followed by a description of methods of investigation of these properties and phenomena at low temperatures. Finally, systematized data from experimental investigations are presented.The last three chapters are concerned mainly with studies of the properties of polymers at low temperatures which have been carried out in recent years by the author and his collaboratorsP .D. Golub and V .E. Sorokin.