The objective of the present essay is to analyze the judicial review applicable to the decisions rendered by the Administrative Council of Economic Defense (Conselho Administrativo de Defesa Econômica - CADE), an agency reporting to the Ministry of Justice legally competent to prevent and repress violations to the economic order. This essay analyzes the extent but not the viability, per se, of the judicial review applicable to CADE s decisions, because it is a principle of Brazilian Law, supported by the Federal Constitution, that the law shall not exclude from appreciation by the Judiciary Branch an injury or threat to a right (art. 5, XXXV, of the 1988 Federal Constitution). For the sake of logic and planning, this essay will initially approach relevant aspects of administrative discretion - one of the most fascinating themes of Public Law and worthy of endless dedication by distinguished jurists such as Seabra Fagundes, Caio Tácito, Afonso Rodrigues Queiró, Eduardo García de Enterría, and Celso Antônio Bandeira de Mello, among others. In the scope of administrative discretion, the relationship between discretionary competence and undetermined legal concepts was an issue that has specially called our attention. This discussion, although still incipient in our legal system, has increasingly been attracting the attention of scholars dedicated to administrative law. Nonetheless, a peaceful understanding has not been reached in this respect yet. The techniques for judicial review of administrative acts - which have been perfected since the establishment of the theories of Deviation of Power and Control of the Reasons of the Administrative Act - will be analyzed subsequently. We will also address the elimination, in the post-positivism era, of the ancient dogma banning the judicial review of the merits of the administrative act, especially in case of violation of legal principles guaranteed by the Constitution and ordinary legislation. After the analysis of the relevant aspects of administrative discretion, we will review the legal principles that govern the economic order, the objectives of antitrust legislation and, mainly, CADE s legal competence. In a specific chapter, we will focus on the legal nature of the decisions rendered by CADE in cases involving anticompetitive practices and in the analysis of concentration acts, which is necessary in order to determine the extent of the judicial review applicable. Special attention was drawn on the controversy regarding the existence or not of discretional powers on the benefit of CADE in granting or denying approval to concentration acts submitted to its analysis. We will also identify situations in which such discretional powers could theoretically take place. In this scenario, the faculty granted to CADE by Law 8,884 of June 11th, 1994 (art. 54, paragraphs 1 and 2) to approve certain transactions which, although potentially harmful to competition, might give rise to efficiencies - in the scope of the meaning attributed to the term by economic law - such as, for instance, technological progress, production increase or diversification, improvement of the quality of goods or services, among others. This essay also indicates how legal scholars have construed such legal provisions, i.e., whether or not such legal provisions actually confer a certain discretion to CADE under those circumstances. Thus, the aim of this essay is to outline the area of administrative discretion, if any, and the extent of the judicial review applicable to CADE`s decisions, taking into consideration the existence of undetermined legal concepts in Law No. 8,884/94, as well as the role played by the principles in guiding the acts performed by any administrative entity. This essay also seeks to delineate the profile of the existing disputes against CADE in Brazilian Courts and to make a critical analysis of our case law. At the end we will make our final consid