The Supreme Court’s recent decision in Ohio v. American Express, in which the Court held that AmEx’s anti-steering provisions do not violate the antitrust laws, was closely watched and elicited strong reactions on both sides. While some celebrated the decision’s recognition of two-sided “transaction platforms” as a relevant market with distinct characteristics and concerns, others criticized it as an unwarranted departure from traditional rule of reason analysis. This panel discussion will explore the treatment of two-sided markets in antitrust law, with an emphasis on how the AmEx decision has been interpreted by courts and invoked by litigants thus far and how it is likely to shape legal theories and analysis in antitrust cases going forward.