For decades, the AAA Yearbook on Arbitration & the Law has served as an outstanding source of guidance on legal developments in the field of Alternative Dispute Resolution. In light of that history, the subject matter covered by this 26th edition is remarkable in the extent that it reflects continued and significant breadth in terms of the ADR issues explored. The continued expansion in the use of ADR for increasingly diverse types of disputes has raised important legal and policy questions, the magnitude of which is perhaps most clearly illustrated by the number of arbitration-related cases the Supreme Court of the United States takes up for review. Those matters are considered here, as are other contemporary ADR-related developments such as class action arbitrations and the enforceability of class action waivers. At the same time, the AAA Yearbook details cases that address what are historically some of the most frequently litigated and recurring issues. For example, courts are commonly presented with arbitrability disputes, the related issue of the allocation of authority among arbitrators and the courts, and questions regarding preemption of the Federal Arbitration Act over a state’s arbitration law. Despite decades of court decisions addressing those matters, courts continue to address still-evolving theories and differing fact patterns that can provide further direction and evolution in the law. The thorough coverage in the AAA Yearbook of these matters, in addition to many others, will serve as a valuable source of information to practitioners, academics, arbitrators, and those with an interest in ADR.