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 perspectives emanating 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 are comprehensively 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 arbitrating mass 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.