The ICSID Reports provide an authoritative collection of investor-State arbitral awards rendered under the auspices of the World Bank's International Centre for Settlement of Investment Disputes (ICSID) and other institutions. 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, and international commercial arbitration, whether advising foreign investors or States. Volume 20 of the ICSID Reports focuses on Attribution of Conduct, including an opening piece by ICSID Secretary-General Meg Kinnear regarding the investor-State application of the International Law Commission's Articles on Responsibility of States for Internationally Wrongful Acts and an overview of the international law on attribution in investment disputes by Professor Jorge E Viñuales. Volume 20 of the ICSID Reports includes summaries, digests and excerpts of decisions rendered between 2009 and 2020 in 16 cases: Bayindir v. Pakistan, EDF v. Romania, Kardassopoulos v. Georgia, Hamester v. Ghana, Tulip Real Estate v. Turkey, Mesa Power v. Canada, Almås v. Poland, Flemingo DutyFree v. Poland, Saint-Gobain v. Venezuela, Ampal v. Egypt, Beijing Urban v. Yemen, Tethyan Copper v. Pakistan, Gavrilovic v. Croatia, Unión Fenosa v. Egypt, Ortiz v. Algeria, and Strabag v. Libya.