This book presents a theoretical-practical study of the procedural rules applicable to five international dispute settlement mechanisms,which have been selected as representative of different areas of international justice Accordingly,the text examines litigation and procedure before the International Court of Justice (ICJ);the Inter-American System for the Protection of Human Rights (IASPHR) as a whole—which includesthe Inter-American Court of Human Rights and the Inter-American Commission on Human Rights (IACHR)—; the International Criminal Court (ICC); the International Center for Settlement of Investment Disputes (ICSID),and the Dispute Settlement Body of theWorldTrade Organization (WTO). Based on the study of primary sources the book presents the procedures followed before each international court or mechanism, thus aiming to provide the reader with a comprehensive, coherent, and systematic study of the judicial and quasi-judicial methods applied at the international level, regarding procedure, competence, jurisdiction, and other procedural and evidentiary aspects, which can be used by juridical operators to guide their work before each international justice mechanism. In addition to the organic and operative parts, this book identifies the main legal problems that arise in the practice of international litigation, and analyzes, from a critical perspective, the operation and development of jurisdictional activities in the international tribunals under study.In a transversal way,it offers a response to the legal problem founded upon the theoretical framework proposed by studies on the fragmentation of international law, particularly based on those carried out by the UN International Law Commission, as well as on different rulings of the studied international tribunals and dispute settlement mechanisms.