A well-functioning antitrust system relies on the effective enforcement of substantive law. Therein lies the challenge.This book is a comparative law study on antitrust enforcement focusing on the differences and similarities between a number of developed and emerging jurisdictions. The developed jurisdictions analyzed are the United States, the European Union and Switzerland. As for the emerging jurisdictions, those examined are China and Brazil. In the first part, the elements which are essential to an efficient antitrust enforcement regime are identified. In the second part, those elements are compared, discussed and assessed.