EU's 2007 enlargement by Bulgaria and Romania is evaluated by applying a simple macroeconomic integration model able to encompass as many of the theoretically predicted integration effects possible. The direct integration effects of Bulgaria and Romania spill-over to EU15, including Austria and the 10 new member states of the 2004 EU enlargement. The pattern of the integration effects is qualitatively similar to those of EU's 2004 enlargement by 10 new member states. Bulgaria and Romania gain much more from EU accession than the incumbents in the proportion of 20:1. In the medium-run up to 2020, Bulgaria and Romania can expect a sizable overall integration gain, amounting to additional ½ percentage point real GDP growth per annum. Within the incumbent EU member states Austria will gain somewhat more (+0.05%) than the average of EU15 (+0.02%) and the 10 new EU member states (+0.01%), which joined the EU in 2004. (author's abstract) / Series: EI Working Papers / Europainstitut