When the General Agreement on Tariffs and Trade (GATT) was concluded in the late 1940s, there was hardly any mention of international transactions in services. At that time, the issue of international trade in services was of minor importance. In addition, attention was initially focused on measures hampering trade at the border. With the principal output of the majority of the sub-sectors of the service industry being “nontangible”, trade impediments relevant for the international exchange of services are of a more subtle nature. These impediments gained importance as the volume of international transactions in this sector increased considerably during the last decade—a development paralleled by the mushrooming of non-tariff barriers in the field of merchandise trade.