On July 3, 2001, the Commission of the European Communities (“Commission”) rejected the proposed $45 billion merger between The General Electric Company (“GE”) and Honeywell International, Inc. (“Honeywell”), which U.S. antitrust regulators had approved. Of the some 400 mergers involving U.S. companies reviewed by the Commission since 1990, only one had ever been barred. In that instance, however, U.S. authorities had also blocked the proposed transaction. Thus, the failed GE-Honeywell merger marked the first time the Commission had blocked a merger involving U.S. companies that had been approved by U.S. authorities. The Commission’s move to block the GE-Honeywell merger brought a firestorm of criticism. This paper seeks to explain the different treatment given to the proposed GE-Honeywell merger by European and American regulators, and explores the reliance by the Commission on an economic theory that has been rejected by the majority of the U.S. antitrust community.