This chapter examines the economics of antitrust, with particular emphasis on how antitrust law affects professional team sports. In the late 1800s, Americans worried about the growing concentration of power in the hands of a few producers such as Standard Oil, American Tobacco, and other large firms that consolidated their holds over industries by merging and acquiring other companies. Other industrial leaders sought to fix prices above those obtained under competition. The Sherman Antitrust Act, enacted in 1890, contains provisions addressing “contract,” “conspiracy,” and “trade and commerce.” This chapter first considers how courts applied the Sherman Act to cases involving professional team sports before discussing the characteristics of professional sports leagues, how owners of professional sports teams reported profits and losses, the issue of player salaries and exploitation, and competitive balance and revenue sharing in professional leagues. It also describes franchise relocation and expansion and how television created demand in sports.