Turko-Greek relations have been strained by a number of conflicting issues such as Cyprus, Continental Shelf, Territorial Waters, the Öcalan affair, and the S-300 Missiles crisis on Cyprus. Until the December 1999 Helsinki Summit, Greece was one of the strong opponents of Turkey's membership in the European Union (EU). However, at the Helsinki Summit of 1999, Greece dropped her negative position permitting Turkey to be declared by the EU as a candidate country. This shift in foreign policy had a direct impact on both Turkey-Greece and Turkey-EU relations. It also represents a major step forward on bilateral relations. The research question tries to explore how did Greek- Turkish relations, disputes in the Aegean and Cyprus entanglement shape Turkey-EU relations and after the Helsinki Summit in 1999 and also with Greek-Turkish rapprochement, how do we expect Greek-Turkish relations to influence Turkey-EU relations. The focus of the book will cover a time period between the Athens Treaty of 1961 and December 2005, when Turkey reached the negotiation phase in her EU accession.