The Permanent Court of Arbitration (PCA) was established at the first Hague Peace Conference in 1899. During the past decade the PCA has progressed from a period of relative inactivity to a previously unsurpassed caseload. In this article the Secretary-General of the PCA reflects on the creation and early development of the PCA, before giving a detailed overview of recent arbitrations conducted under PCA auspices. The first part of this review, concerning treaty-based arbitration, analyses the role of the PCA in the resolution of disputes under the United Nations Convention on the Law of the Sea, illustrated by the arbitrations conducted in the Guyana/Suriname, Barbados/Trinidad, Malaysia/Singapore, and Ireland/United Kingdom (MOX Plant) disputes. The second part, which focuses on ad hoc arbitration, outlines the recently concluded arbitrations in the Iron Rhine (Belgium/Netherlands) and Eritrea/Yemen cases, as well as the work of the Eritrea–Ethiopia Boundary Commission and Claims Commission.