The ICSID Reports provide an authoritative published collection of investor-State arbitral awards and decisions rendered under the auspices of the World Bank's International Centre for Settlement of Investment Disputes (ICSID), pursuant to other bilateral or multilateral investment treaties such as the North American Free Trade Agreement (NAFTA) and the Energy Charter Treaty (ECT) or involving investment contracts entered by States. These decisions, which are fully indexed, make an important contribution to the growing body of jurisprudence on international investment law. The ICSID Reports are an invaluable tool for practitioners, scholars and government lawyers working in the field of public international law, investment treaty arbitration, international commercial arbitration, or advising foreign investors or States. Volume 18 of the ICSID Reports focuses on Defence Arguments in Investment Arbitration, including an opening piece from leading scholar and practitioner Professor Jan Paulsson, a founding partner of Three Crowns LLP, and a preliminary study by Professor Jorge E Vinuales, Harold Samuel Chair of Law and Environmental Policy at the University of Cambridge. Volume 18 of the ICSID Reports includes summaries, digests and excerpts of decisions rendered between 2007 and 2018 in 20 cases involving States from across Africa, Asia, Europe and the Americas, reflecting the breadth of defence arguments in contemporary practice: Sempra v. Argentina, Continental Casualty v. Argentina, Cargill v. Mexico, Mobil v. Canada, Bankswitch v. Ghana, Yukos v. Russia, von Pezold v. Zimbabwe, Quiborax v. Bolivia, General Dynamics v. Libya, Philip Morris v. Uruguay, Devas v. India, Churchill v. Indonesia, Urbaser v. Argentina, Orascom v. Algeria, Karkey v. Pakistan, E energija v. Latvia, Mercer v. Canada, Antaris v. Czech Republic, ENKA v. Gabon, and Cortec v. Kenya.