A Practice Note surveying the relevant antitrust statutes and recent enforcement actions involving most favored nation clauses (MFNs), also known as most favored customer clauses. This Practice Note discusses the antitrust risks associated with MFNs, including under the Sherman Act, theories of competitive harm involving MFNs, such as collusion and price stickiness, and antitrust agency enforcement actions involving MFNs. This Practice Note also offers practical tips for counsel analyzing an MFN under the antitrust laws.