Abstract. Opposition to the European integration project can stem from many different sources, but one that appears to be fairly fundamental is the threat that the European Union (EU) poses to long-established national identities. This contention may in fact appear to be so trivial as to make it uninteresting to the social science community. However, this article analyses the degree to which EU citizens do indeed feel their national identities to be under threat by the EU and the effect of such fear on general feelings about the integration process. The impact of fear of loss of national identity due to integration is then compared to the impact of other potential sources of variation in support for the integration project. The results indicate that while large proportions of EU citizens do indeed fear that the EU is threatening their national identity and culture, the effect of this fear on attitudes toward the EU is not all that substantial and other factors play an equal or greater role in explaining individual-level opposition to the EU.