Merger guidelines in the United States are a set of internal rules promulgated by the Antitrust Division of the Department of Justice (DOJ) in conjunction with the Federal Trade Commission (FTC). These rules have been revised over the past four decades. They govern the process by which these two regulatory bodies scrutinize and/or challenge a potential merger. Grounds for challenges include increased market concentration and threat to competition within a relevant market. The merger guidelines have sections governing both horizontal integration and vertical integration.