Abstract In 2002, the General Court famously annulled three merger prohibitions under the EC Merger Regulation because of serious errors of assessment. Amongst other things, it held that the Commission had ignored economic theory. Consequently, the Commission announced radical changes to its approach to ensure that future assessments would be based on rigorous economic and econometric analysis. This contribution examines the changes introduced by the Commission's "more economic approach" to EU merger review. An analysis of the Commission's merger guidelines and decisions reveals that the core of the new approach by no means lies in the use of econometric analyses and complex theories of microeconomics. Its essence rather lies in aligning the purpose of EU merger law with the consumer welfare aim of modern industrial economics. On the basis of this new legal objective, the Commission reinterpreted the substantive test of EU merger law as containing an unwritten consumer harm requirement and reconsidered the role of efficiency effects. The Commission's new concept of harm is not entirely compatible with the case law of the Court of Justice, which continues to adhere to its "less economic" concepts of the 1970s. Moreover, the Commission's attempts to reconcile the two worlds have resulted in theories of harm that are ambiguous and therefore detrimental to legal certainty.