This article is concerned with the ongoing debate on process and production methods (PPMs) and the extent to which existing GATT 1994 articles and WTO agreements are able to deal with these issues. The article provides an overview of GATT articles III.4 on like products and XX on general exceptions as well as the SPS and TBT agreements. It then summarises four recent GATT/WTO trade dispute cases involving PPM issues: tuna-dolphin; shrimp-turtle; gasoline standards; and asbestos. The WTO panel and appellate body decisions in these cases are analysed with regard to articles III.4 and XX in the context of the evolution of WTO case law with respect to PPMs. Inferences are also drawn concerning the likely implications for a potential trade dispute over GM products between the EU and the United States. The article then draws some policy conclusions.