In July 2003, the European Parliament voted on amendments to the European Unions (EU) system of regulation for agricultural biotechnology, most notably the rules for mandatory labeling of food products that contain traces of genetically modified (GM) ingredients. The expectation is that approval of these changes in EU regulations will result in the moratorium on approval of new GM crops, formalized by the Council of the European Union in 1999, being lifted. Despite the approval of these amendments, in August, the US, along with Canada and Argentina, requested the formation of a WTO dispute panel to make a ruling on the EUs failure to approve marketing of a number of GM crops.This paper addresses the issue of whether there is any legitimacy in the EUs precautionary approach to biotechnology regulation, or whether their regulatory approach is trade distorting, and, hence, likely to be found in violation of WTO agreements. First, the background to the debate in the EU and US over biotechnology is reviewed, paying particular attention to recent public discussion in the UK where the government has undertaken an extensive public consultation process over regulation of GM crops. Second, the EUs approach to biotechnology regulation is outlined and compared to that in the US, and the analytical foundations of the precautionary principle are reviewed. Third, how GM regulations fit into the rules of the WTO is outlined, along with a discussion of the nature of the USs WTO filing.