In the current discourse it is frequently stated that in the course of European integration and globalisation we witness more intensified and more frequent transactions spanning across national borders. These assumptions relate not only to transactions in the economic sphere or to forms of political co-operation, but to the individual lifeworlds as well. Yet concerning the latter dimension, research into the patterns and dynamics of interpersonal interaction, relationships, and forms of mobility across national borders is scarce. This paper is a contribution towards filling this research lacuna. It addresses the question of the extent to which horizontal Europeanisation, understood as different forms of individual cross-border activities within the European Union, depends on characteristics at the country level. From a comparative perspective we will analyse the transnational mobility and cross-border networks of European citizens within a European context. Empirically, we refer to data from the Eurobarometer 65.1 (2006), which allows us to answer the question how certain contextual variables, such as internationalisation, modernisation, and characteristics such as the respective country's geography, affect people's participation in cross-border activities. Based on a sample of 25 European countries, we will demonstrate that geographic characteristics drive social transnationalism less than internationalisation, Europeanisation, and modernisation, which contribute to a proliferation of individual transnational activities across the European Union.