A Practice Note discussing how the US antitrust agencies may share parties' confidential information provided during the merger review process with federal, state, and non-US enforcement agencies, including information submitted under the Hart-Scott-Rodino Act (HSR Act) through compulsory process or voluntary submissions. This Practice Note provides advice to counsel making confidential submissions to the Federal Trade Commission (FTC) and Department of Justice (DOJ), including on whether to waive confidentiality to allow those agencies to share materials with other enforcement agencies.