This report reviews the challenges facing U.S. agricultural biotechnology products in international trade. GAO found that new regulations and guidelines that may restrict U.S. exports of crops with a large biotech component are being enacted or considered by some U.S. trading partners and are also under discussion in various international organizations. These actions address approval, labeling, and traceability of agricultural biotech products. U.S. corn and soybean exports are most threatened by new foreign regulatory measures because of their biotech content. Although U.S. soybean exports have not yet experienced disruptions, U.S. corn exports have been largely shut out of the European Union (EU) market because U.S. farmers are producing some biotech varieties that have not been approved for marketing in the EU. U.S. agricultural biotech exports face several significant challenges in international markets. First, as the single major producer of biotech products, the United States has been relatively isolated in its efforts to maintain access to markets for these products. Second, in many parts of the world, consumer concerns are growing about the safety of biotech foods, which have led key market countries to implement or consider regulations that may restrict U.S. biotech exports. Another challenge is that U.S. industry combines conventional and biotech grain in the distribution chain. Consequently, foreign regulations governing biotech varieties could affect all U.S. exports of these commodities. Finally, as international negotiations in Codex Alimentarius and elsewhere take on greater importance, the U.S. government faces increasing demands for staff resources and coordination among the multiple agencies involved in biotech trade issues.