One of ICSID arbitration's perceived strengths - and one of its most charac-teristic features - is its internal mechanism for reviewing arbitral awards by ad hoc committees specifically convened by ICSID. There have been only seven ICSID annulment decisions, five of which are published. The two earliest decisions -annulling the awards in Klöckner v. Cameroon (1985) and Amco v. Indonesia (1986) - were poorly re-ceived, leading some commentators to cast doubt on the effectiveness of ICSID arbitration as a whole. This criticism subsided following the partial annulment decision in MINE v. Guinea (1989) and the unpublished decisions dismissing the applications to annul the awards rendered in the resubmitted Klöckner (1990) and Amco (1992) disputes. Ten years then passed before, in 2002, the next ICSID annulment decisions were rendered, with the dismissal of the application in Wena v. Egypt and the partial annulment of the award in Vivendi v. Argentina. These landmark decisions have recently been published, and it is their impact that provides the focus for this work.