In 2001 Ireland commenced litigation against the United Kingdom (UK) over the construction and operation of a plant to produce mixed oxide fuels at the Sellafield nuclear complex in north-west England. This litigation, which had been only partially concluded at the time of writing, raises a series of fascinating and often complex issues of both international and EU law. These include the potential for overlapping jurisdiction between different international tribunals; the division of competence between the EC and its Member States in relation to participation in treaties; and the use of litigation as a strategy for settling inter-State disputes. The aim of this article, apart from giving a snapshot of the position that the increasingly tortuous course of this litigation had reached by January 2004, is to explore these issues. The article begins by setting out the background to the litigation and giving a quick overview of its course so far. It then explores in more detail the questions of overlapping jurisdiction of international tribunals and of EC law raised by the litigation, before concluding with a few, rather speculative, thoughts about Ireland's choice of litigation as a strategy.