The responsibility for protecting U.S. agriculture from pests and diseases is assigned by the Federal Plant Pest Act (FPPA) to the Animal and Plant Health Inspection Service (APHIS) of the Department of Agriculture. The Plant Protection Act (Title 7 U.S.C. Sections 7701 et seq.) gives Aphis statutory authority over genetically modified organisms (GMO), in effect assigning to APHIS a related responsibility of determining whether a genetically altered plant, crop, or tree is likely to pose unacceptable risks to the environment. Although APHIS has considerable experience with crop plants, it has only limited experience with trees. Yet the possible benefits of applying genetic engineering to trees are substantial and include industrial wood production and environmental uses, such as toxic remediation and species restoration. This report focuses on the Plant Protection Act (PPA) and related regulations as they have been applied to timber transgenic trees.