This paper aims firstly to determine the factors that lead multinational firms to internalise their international exchanges and secondly to analyse the impact of the implementation of the European Single Market on their strategies. This study is based on the “Industrial Globalisation” survey conducted by the French statistics institutes in 1993 and in 1999. With regard to French agro-food trade, the results show that there has been an increase in intra-firm trade within the EU borders and the European MNEs’ networks. The main determinants of intra-firm trade are the firms’ need to generate economies of scale and to protect and exploit their “firm-specific advantages” related to the technology and to the nature of the product. The model not only reveals the groups’ strategy to penetrate the EU markets and to bypass borders, but it also sheds light on the role and the development of intra regional networks of subsidiaries.