International organizations are unusual creations: generated by and for their member states, at the same time they often have to compete with those very states that created them. This complicated relationship often leads to some uncertainty in the law relating to international organizations: the legal argument of an organization will often be counterpointed by an equally valid argument from a member state. Professor Jan Klabbers is mindful of this complex relationship in his comprehensive analysis of international institutional law. As well as describing the law as it applies to legal institutions in chapters that include dispute settlement, financing and treaty-making, Klabbers looks forward to a re-appraisal of the status of international organizations. This is a key textbook for advanced-level students of law and of international relations.