The goal of Section 1 of the Sherman Act (the Act) is to “promote and protect free-market competition” by defining “every contract, combination...or conspiracy” that is in restraint of interstate or foreign commerce as illegal. The expansive and open language of the Act has resulted in a flurry of extensive Federal common law in both criminal and civil courts. This article explores the criminal aspects of antitrust enforcement by first reviewing the four elements of a criminal antitrust violation as they are defined in Section 1 of the Act: conspiracy, restraint of trade, interstate nexus, and intent. Once the government has discovered a conspiracy that violates antitrust laws, a number of criminal defenses may be raised, including withdrawal from conspiracy, statute of limitations, and double jeopardy defenses, along with single entity, respondeat superior, meeting competition, and State action immunity defenses. Each of these defenses is discussed in turn in addition to discussions on petitioning the government, regulated industry, and foreign commerce defense strategies. Historically, State and Federal agencies have handled the criminal enforcement of antitrust violations. Aspects of Federal, State, and international enforcement are described along with the penalties for antitrust violations, which in recent years have included ever-increasing monetary fines. Finally, recent developments in international cooperation regarding antitrust enforcement are reviewed including the development of the International Competition Network (ICN), established largely in response to the challenges in antitrust enforcement that have been created by the increasing globalization of crime. Footnotes