The harmonisation of the laws of Member States in various areas of private law constitutes an important element of the European Union integration process. The principal legislative mechanism used to achieve this harmonisation is the directive. Effective harmonisation of national laws can only be achieved if the Community legislation is applied in the same way in the different national legal systems. Many of the challenges in ensuring a harmonised application of community legislation are connected to issues of legal language. Amongst other examples, this paper will use the European directive on product liability (la responsabilité du fait des produits défectueux) as an illustration of the various language issues raised and the solutions available to ensure an effective level of harmonisation. This will be done through a study of the English and French versions of the directive, and by considering the experience of the implementation of the provisions of the directive in French and English law.