The debate over the value of private antitrust enforcement long has been heavy with self-serving assertions by powerful economic interests, but light on factual evidence. To help fill this void we have been conducting research for several years on a variety of empirical topics. This article develops and then explores the implications of a startling finding. Even those who do not deride private enforcement usually believe its only function is to compensate victims of antitrust violations by modest amounts. Significant deterrence is commonly thought to be the effect only of government enforcement, especially criminal enforcement. Our article's conclusion that the amounts of payouts in private cases are actually staggeringly high—so high that they deter anticompetitive conduct more effectively than the criminal fines and prison sentences resulting from Department of Justice cases—is thus the opposite of the consensus within the antitrust community. Indeed, we hope this article causes many in both the United Sates and in Europe to reevaluate their views as to the overall efficacy of private antitrust enforcement.