Comprehensive study of the economic aspects of an antitrust policy. The first chapters discuss general aspects of competition policy (history and objectives) as well as the issues that are common to the dimensions of said policy (market power, welfare, market definition and determination of market power). Subsequently, the author delves into each of the dimensions of the policy (posters, abuse of a dominant position and concentrations) with a similar approach. It illustrates the monopolies, the competition, the benefits and disadvantages of the different economic models; it delimits the norms for valuation and prices, and the laws around abusive practices in the market; it deals with the mergers of companies, the origin, their effectiveness, the schemes to follow; it reviews prices of different markets, internally and between them, it analyzes current practices between countries with stable economies and emerging ones, the interaction between them, the movements and the rules that continue within the competency model.