Conglomerate mergers are the most prevalent and the most controversial of the three types of mergers-horizontal, vertical, and conglomerate. The controversy stems in part from the marketing possibilities inherent in some conglomerate mergers, but it also stems, unfortunately, from basic misconceptions of the meaning of these mergers. The present article, based on an analysis of conglomerate mergers in the history of the 1950 Amendment to Section 7 of the Clayton Act, indicates the nature and origin of the disagreement on the meaning. The author presents criteria for determining when a merger is, in part or whole, a conglomerate merger.