This article examines the extent to which state officials are subject to prosecution in foreign domestic courts for international crimes. We consider the different types of immunity that international law accords to state officials, the reasons for the conferment of this immunity and whether they apply in cases in which it is alleged that the official has committed an international crime. We argue that personal immunity (immunity ratione personae) continues to apply even where prosecution is sought for international crimes. Also we consider that instead of a single category of personal immunity there are in fact two types of such immunity and that one type extends beyond senior officials such as the Head of State and Head of Government. Most of the article deals with functional immunity (immunity ratione materiae). We take the view that this type of immunity does not apply in the case of domestic prosecution of foreign officials for most international crimes. However, we reject the traditional arguments which have been put forward by scholars and courts in support of this view. Instead we consider the key to understanding when functional immunity is available lies in examining how jurisdiction is conferred on domestic courts.