Patricia R. Zeigler

Of Counsel
Antitrust & Competition

Patricia Zeigler, Of Counsel in the Washington, D.C., office, focuses her practice on antitrust law with particular emphasis in Hart-Scott-Rodino Act compliance and counseling.

Her experience includes advising clients on issues of reportability and interpretations of the Hart-Scott-Rodino Antitrust Improvements Act and its regulations. Ms. Zeigler also has expertise in the applicability of foreign premerger requirements and filings with regulators in the European Union, Asia and Canada.

Ms. Zeigler served as antitrust counsel to two large industry groups establishing Business to Business exchanges for E-commerce transactions. She currently serves as general counsel to five large trade associations in a wide range of industries. In addition, Ms. Zeigler works with trade groups to set up and run joint purchasing organizations.

Prior to joining the firm, Ms. Zeigler practiced antitrust law for over a decade with Pillsbury Madison & Sutro.

In addition to being admitted in the District of Columbia, Ms. Zeigler is also admitted in California (inactive).

Patricia Zeigler
Select Publications
  • Co-author, supplement to the International Mergers: The Antitrust Process treatise by J. William Rowley and Donald I. Baker.
  • Contributor, publication posted on the Federal Trade Commission website summarizing the answers to the twenty questions most frequently posed to the Premerger Notification Office staff (
  • Served on a task force with members of the Premerger Office in redrafting the Regulations implementing the Hart-Scott Rodino Antitrust Improvements Act of 2000.
Admitted In
  • District of Columbia

  • J.D., with honors, University of San Francisco School of Law, 1983
  • B.A., Oberlin College, 1980
  • District of Columbia Bar

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