Adapted from a January 26 presentation made at the Association of American Feed Control Officials Midyear Meeting in Phoenix, Arizona.The Office of Surveillance and Compliance in the Center for Veterinary Medicine (CVM) is responsible for reviewing data on genetically modified plants intended for use in animal feed. The Federal Food, Drug, and Cosmetic Act, which delineates FDA's regulatory authority for foods, defines food as articles used for food or drink for man and other animals. The Act, however, does not require pre-market clearance of food and thus, many genetically modified plants do not require formal pre-market review by the FDA as they are food. The first modified plant evaluated by the Agency was the Calgene FlavrSavrTM tomato which has improved ripening qualities. Calgene requested FDA regulation of the inserted marker gene product, aminoglycoside 3'-phosphotransferase II, an enzyme, as a food additive due to the novelty of the technology. This enzyme is encoded for by the kanr or APHII gene. FDA actually regulates the gene product or its intended effect, not the inserted DNA itself. Thus, it is the gene product, aminoglycoside 3'-phosphotransferase, that was approved in 1994 as a food additive for food and feed usages in tomato, oilseed rape, and cotton (21 CFR 173.170 and 573.130). In 1992 the FDA published a Statement of Policy in the Federal Register for Foods derived from New Plant Varieties. This policy applies to both genetically modified plants and those derived through other means. The 1992 policy sets out how the developers of new plant varieties should evaluate the safety and nutritional value of these foods. This science-based evaluation process is determined by the characteristics of the food, not its method of development. One primary focus is to determine if there are any unexpected effects in the new variety due to the genetic modification. These effects could include: 1) changes in toxicant or anti-nutrient levels; 2) changes in nutrient concentrations; and 3) alterations in allergenicity, i.e., the unintended movement of an allergenic protein from one food to another. The policy also addresses how the developers assess the safety of introduced proteins and other novel substances, the safety of any modified carbohydrates, fats, or oils, and also the products coded for by marker genes. The use of antibiotic resistance marker genes is also addressed in an Agency draft guidance document, which published in 1998. Plant developers can continue to use antibiotic resistance marker genes, but the guidance urges them to consider current medical practices and whether usage of the marker gene could compromise antibiotic effectiveness.