When the Supreme Court hears Bell Atlantic Corp.v. Twombly this fall, it will confront both a fundamental issue of pleading law in an antitrust context and an important question of substantive antitrust law at the pleading stage. The case could throw open the door to vexatious litigation, or the Court could affirm district courts’ authority to dismiss abusive lawsuits—before plaintiffs have the opportunity to impose massive discovery costs—by insisting that plaintiffs plead facts that demonstrate an entitlement to relief. The case could impose a tax on ubiquitous business conduct by turning all “parallel” conduct into fair game for enterprising plaintiffs’ lawyers, or the Court could protect the important antitrust principle that parallel but unilateral conduct is lawful, thereby reinforcing a trend of antitrust decisions that preserve individual economic actors’ freedom to behave in ways that are efficient without concern about baseless but costly litigation.