In a historic moment, the European Council decided in its December 2004summit to open accession negotiations with Turkey on 3 October 2005. Even thoughTurkey has been on the borders of the European Union since its AssociationAgreement in 1963, there has always been a degree of ambivalence towardsTurkey’s membership. This paper proposes that the following factors willdetermine, to a large extent, both the nature of Turkey’s accession negotiations withthe EU and whether Turkey will ever accede to the EU as a full member. Thesefactors are: the institutional restructuring in the EU, in other words the changesthat the Constitutional Treaty brings to the functioning of the EU and the securitychallenges for European and western security, particularly important here is theIslam vs. Europe divide