This article examines the extraterritorial application of Pt IV of the Competition and Consumer Act 2010 (Cth). It considers the general principles governing the extraterritorial operation of statutes, the extension of Pt IV to conduct engaged in outside Australia by residents or bodies corporate carrying on business in Australia, how concepts such as markets and competition may have extraterritorial operation, and how the cartel provisions of the Act potentially apply to cartel provisions made or given effect to outside Australia. The article commences with a discussion of some general principles limiting the territorial application of statutes, including the constitutional sources of the power to legislate extraterritorially, followed by a discussion of the tensions between comity and the effects doctrine under American law, before considering how overly wide extraterritorial operation of antitrust laws by one nation can result in blocking statutes by others to prevent incursions into their sovereignty. The author then considers particular provisions in the Act that have extraterritorial operation, including the definitions of “market” and “competition”, before discussing the extraterritorial application of the Act provided for in s 5 (with particular emphasis on the carrying on business requirement). Finally, the author considers the extraterritorial operation of the cartel provisions of Div 1 of Pt IV and briefly discusses the requirements for service out of the jurisdiction. Limited space precludes consideration of international cooperation agreements or other potential means of harmonising world antitrust laws.