In Jurisdiction and Admissibility in Investment Arbitration, Filippo Fontanelli offers an analysis of the subject for practitioners and scholars. The author undertakes two converging studies: first, the practice of investment tribunals is surveyed to provide a representative overview of how jurisdiction and admissibility operate in arbitration proceedings. Second, these concepts are studied in the wider framework of public international law litigation, in the attempt to solve the definitional issues, or at least trace them back to their theoretical background.The analysis shows that the confusion prevailing in investment arbitration is largely a legacy of the comparable confusion that affects the notions of jurisdiction and admissibility in all kinds of dispute settlement under international law. Whilst the confusion is often irrelevant in the practice, some instances arise where it affects the outcome of the proceedings. The essay discusses some of these instances and recommends adopting a novel approach, which hinges on judicial discretion as the critical element of admissibility.