Editors' Summary: Phytosanitary systems have been used for many years, but it is only recently that they have received careful and detailed international scrutiny to ensure that they are fair, effective, and well documented, with appropriate internationally accepted standards. This Article examines the development of current practices and applications of phytosanitary measures, including the legal systems backing their use and the broader applicability of these systems to the maintenance of the natural environment and the biodiversity of species. The Article is excerpted from Harmful Invasive Species: Legal Responses (Marc Miller & Robert Fabian eds., Envtl. L. Inst. 2004). The book, now available from the Environmental Law Institute, describes the law and policy regarding harmful non-indigenous species in six countries: Argentina, Germany, New Zealand, Poland, South Africa, and the United States. The book also addresses three international and cross-cutting dimensions of harmful non-indigenous species policy: quarantine systems, trade issues, and the special concerns raised by genetically modified organisms. For more information and to order, visit http://www.elistore.org/books_detail.asp?ID=10930.