This introduction presents an overview of key concepts discussed in subsequent chapters of this book. In recent years, there have been various approaches to the analysis of shrinking cities. The book is divided into four distinct parts dealing with a wide range of themes. The first part consists of one global chapter and two regional chapters, one on the European Union, the other on Latin America. The second part is a medley of countries from all over the world. The fourth part of the book looks at two general issues: the environmental benefits of shrinking cities and whether compact or sprawling cities are a better antidote to urban shrinkage. Three cities are examined in Europe, but none in Great Britain nor France. The evolutionary theories demonstrate how the life-cycle of products and sectors could well lead to overspecialisation, backwardness and difficulties to adopt changes at the saturation stage.