This chapter surveys the existing empirical literature on international arbitration. It focuses on quantitative rather than qualitative empirical studies, and covers studies both of international commercial arbitration and international investment arbitration. The chapter first describes empirical research on the use of arbitration to resolve transnational disputes—in particular, the extent to which parties use arbitration clauses in international contracts, why they do so, and the frequency of international commercial and investment arbitration proceedings. Empirical studies have also examined an array of topics about the procedures in international arbitration. The empirical evidence typically comes from surveys or observational studies of commercial and investment arbitration proceedings. The chapter then considers empirical insights on selected topics such as the cost and length of arbitration proceedings, the size of arbitral tribunals, interim measures, multi-party disputes, challenges to arbitrators, the role of tribunal secretaries, and the use of mediation. It also looks at empirical studies on the applicable law in international commercial arbitration; the demographics of international arbitrators; and compliance with and enforcement of international arbitration awards.