The innovative contributions of the Italian Marginalists - Pareto, Pantaleoni, De Viti de Marco and Barone, to economic theory have previously been overlooked. This is the first book to deal with the history of the theory of market power and of its relation with competition, focusing on the distinct intellectual tradition that is Italian Marginalist economic thought. Monopoly Power and Competition is a vital resource for historians of economic thought, as it explores a relatively untouched area of microeconomics that sheds light on the theories surrounding monopoly power and barriers to entry.