We will study both antitrust law and antitrust economics. Antitrust law governs the accumulation and exercise of market power. It prohibits both monopolization and agreements in unreasonable restraint of trade such as price fixing. It also prohibits anticompetitive mergers and a variety of specific competition problems such as exclusive dealing or tying arrangements. Deciding what qualifies as "monopolization," what qualifies as an "unreasonable restraint of trade," what qualifies as "anticompetitive," and more generally how to interpret the prohibitions of antitrust law invariably involves economic analysis. Such economic analysis commonly goes by the name "antitrust economics".