In their opinions on the FTC’s challenge to the proposed merger of Tronox and Cristal, the federal and administrative courts broke ground in a number of areas that have important implications for antitrust practitioners. In this article we discuss what we see as four key aspects of these decisions, and explain their potential implications for the federal antitrust agencies and the private bar. These key aspects are: (1) clarifying the importance of evidence directly addressing customer responsiveness when defining relevant markets; (2) providing support for theories of harm focused on strategic withholding of output; (3) showing that arguments about Chinese expansion must be more than theoretical to overcome competition concerns; and (4) demonstrating that the agencies remain willing and able to bring—and win—coordinated effects cases.