The evolution of the Single Market is both a legal process and a political process. The concept of a Single Market requires the elimination of all barriers to inter-state trade and all national prohibitions on establishment and the ultimate harmonisation of laws and regulations throughout the Community. The political reality is that vested interests, both of national governments' and of trade and professional organisations,' seek to delay the creation of this kind of Single Market. In these circumstances the choice facing the Community may be seen as being that between delaying the Single Market process until these obstacles can be overcome or reaching a pragmatic compromise by allowing the retention, at least temporarily, of some of the existing barriers.3 If it is accepted that some barriers can be retained, the next problem is to identify which these are. Some barriers must be seen as entirely incompatible with the Single Market, whilst others may be regarded as tolerable. In the first instance the European Court of Justice may be called upon to decide which barriers fall into which category.4 It is, though, far from clear that the Court is the appropriate institution to develop an internal EEC Commercial Policy in this way. Fundamentally the task is one which ought to be performed at a political rather than a judicial level. Even if 'legitimate' trade barriers can be identified, there is the further issue of deciding whether these are to be imposed at Community level or whether the decision-making authority is to be delegated to individual Member States, with the inevitable consequence that there will be different regimes in different Member States. This article looks at the ways in which these problems are being approached in a number of different areas of activity and considers whether any pattern can be seen to be emerging in the development of the Single Market. An important theme in this examination is the relative effectiveness of different interest groups in securing the recognition of particular trade barriers as legitimate and in obtaining for themselves the power to determine the content of those barriers. This point is related to the crucial distinction between changes which are intended to make it easier to conduct business on a Community-wide basis (referred to here as 'facilitative legislation'), and changes which are designed to regulate business activity, usually in the interests of protecting groups such as consumers and employees (referred to here as 'protective legislation'). This article proceeds by examining the distinction between lawful and unlawful trade barriers, before considering the ways in which lawful barriers are being treated in the run up to 1992. It will be seen that the interaction of the various interest groups is leading to the adoption of a number of different approaches to these problems.