This paper scrutinizes the impact of the fifth EU enlargement on the changes of ASEAN’s patterns of trade by focusing on ASEAN-7’s exports at the sectoral level using a qualitative framework. This approach differs from other conventional studies that look at the impact of the enlargement on either the EU or the new EU member countries. Two new trade indices are proposed in this paper, namely the Rivalry Threat Index (RTI) and the Export Threat Index (ETI). The analysis is conducted at the 3-digit level of SITC Rev.3 industry for the years 1997, 2000, 2003 and 2006. The findings indicate that: the degree of threat on ASEAN exports (emanating from the new accession countries) to the EU15 market are not significantly high in general; the effects on the major exporting products from ASEAN to the EU15 (SITC7 and 8 categories) are fairly high; ASEAN countries may face a very intense degree of export threat in the services sectors. Nonetheless, the major trade partners of ASEAN (i.e. the USA, Japan and China) may be able to help ASEAN neutralise the export threat on the EU15 market by acting as a shock absorber for ASEAN exports.