This paper presents quantitative estimates of the trade and welfare effects of the entry of Greece into the EU and presents a tool for assessing the impact of the Central and Eastern European Countries' accession to the EU. Both the static and the dynamic effects of the entry of Greece into the EU are examined. When looking at the static effects, it is shown that there was a “net”trade creation of about USD 1.6 billion, which accounted for approximately 4.4% of the GDP of the year before accession. It has also been found that 86% of the total trade creation was internal trade, while 84% of the entire trade diversion was external trade diversion, these being results that accord with the theory of the customs union. When we make an assessment of the dynamic effects, we can see that Greece's EU entry had mixed reactions in different sectors: for about two-thirds of the examined sectors we find that Greece's integration into the EU was desirable - in general, however, the integration indices found are close to being the same, thereby showing that the dynamic effects of the country's EU entry have been minimal.