This publication from the International Bureau of the Permanent Court of Arbitration (PCA) presents a collection of studies on the key issues found in complex international commercial and investment disputes. Renowned authors from Europe and North America consider issues from perspectivesemanating from both the Anglo-American and Continental European legal systems. The authors consider international multiparty arbitration and its attendant problems from both a conceptual and practical perspective, beginning with the overarching legal problems of determining the proper parties to the arbitration and the ambit of contractual consent. Topics which arecomprehensively examined include: Joinder of parties and consolidation of arbitral proceedings; the challenges of administration of multiparty arbitrations; investment arbitration involving multiple parties and multiparty issues in investor-state arbitration; classwide arbitration and arbitratingmass investor claims; lessons that can be learnt from mass claims processes; and enforcement issues. The book also includes a practitioner-oriented discussion of multiparty arbitration in the construction industry.