Anticompetitive Effect by Judge Cudahy and Mr. Devlin focuses on a critical issue in antitrust jurisprudence: whether anticompetitive effect should be evaluated under an “aggregate welfare approach to competition” or under a “consumer welfare” approach. What hangs in the balance is the future efficacy of both public and private enforcement. This Comment traces the history of antitrust jurisprudence, and, in particular, the trend since the mid-1970s of the original intended targets of antitrust regulation ascending to positions of authority and becoming, in essence, the regulators. This Comment argues that this history demonstrates that antitrust law has become an instrumentality for preserving the very concentrations of economic power the antitrust laws were enacted to prevent, remedy, and limit. This has occurred not only through radical changes in substantive antitrust law, supported by economically suspect, if not discredited, free market Chicago school dogma, but also through equally radical changes in procedural law, which have made enforcement litigation into an obstacle course for plaintiffs and considerably narrowed the federal courthouse doors. The choice between adopting the aggregate welfare approach or the consumer welfare approach in determining anticompetitive effect will have profound practical consequences in antitrust enforcement. Only by choosing the aggregate welfare approach, as Judge Cudahy and Mr. Devlin urge, is there a possibility of halting or reversing the historical trend and revitalizing antitrust enforcement.