A Practice Note discussing joint purchasing arrangements, including group purchasing organizations (GPOs). It addresses the formation and operation of GPOs, including the appropriate legal standards (rule of reason or per se), efficiencies, and antitrust risk. The Note also addresses the safe harbors in the Antitrust Guidelines for Collaboration Among Competitors and the Statements of Antitrust Enforcement Policy in Health Care issued by the Antitrust Division of the Department of Justice (DOJ) and the Federal Trade Commission (FTC). The DOJ withdrew the Statements in February 2023, and the FTC withdrew the Statements in July 2023.