Firms in an oligopolistic market can exercise market power to maximize profits. This can lead to a government response to protect consumers: either to ensure that they have sufficient access to the products, or to limit the prices they have to pay. This reaction can take two forms: government regulation or antitrust supervision. We study these two answers. The course also aims to familiarize students with the techniques and tools of empirical industrial organization used by economists in market analysis firms to calculate optimal prices, to analyze the impact of the introduction of new products or mergers of firms and examine the impact of advertising on demand.