This original new book offers a comprehensive and engaging perspective on the theory of vertical differentiation. It enables the reader to grasp the key concepts and effects that product quality has both on firms' behaviour and market structure, and the ways in which this relationship has evolved. With contributions from prominent figures in the field, the book investigates a number of important topics, such as the choice of the optimal product range, profit sharing, the existence of equilibrium in duopoly games, positional effects attached to status goods, international trade, collusion, advertising and the dynamics of capital accumulation for quality improvement and product innovation. Using both static and dynamic approaches, these aspects are assessed in relation to the manifold issues of regulation, competition policy and trade policy. Product differentiation and its influence on consumer behaviour and the performance of firms is a core topic in the existing literature in the fields of industrial organization, international trade and economic growth. This book will be an essential read for researchers, students and professional scholars working in these areas, especially those with an interest in antitrust regulation.