We study the formation of bi-national marital unions among partners from Switzerland and the European Union (EU) 15 countries as one indicator of the Europeanisation of Swiss Society. The result of our empirical analysis shows that there is in fact no clear increase of such bi-national marriages over time. However, there are two structural conditions fostering EU15 marriages. One is that Swiss living close to the country's border have a higher propensity to marry a person from across that border compared with other Swiss. The other is that the greater the size of the foreign population in a Swiss canton, including a larger number of EU15 nationals, the more likely is a Swiss to have a spouse from an EU15 country. These results suggest the conclusion that a rise in EU15 marriages is still to come as the number of foreigners from these countries is increasing and also border regions become more important because of a continuing rise of commuters from neighbouring countries.