An agreement between two or more businesses operating at different levels of production or distribution in the market, such as an agreement between a manufacturer and a distributor or a wholesaler and a retailer. Compare this to a horizontal agreement. The distinction between the two is important under antitrust laws, because the nature of the relationship between the parties may determine how potential violations are evaluated.

For examples, see Practice Note, US Antitrust Laws: Overview: Horizontal or Vertical Restraints.