into the environment is tantamount to the introduction of a new organism.

The original 1987 APHIS regulations were later to exempt Escherichia coli strain K-12, sterile strains of Saccharomyces cerevisiae, asporogenic strains of Bacillus subtilis, and Arabidopsis thaliana from permitting requirements for interstate movement under certain specified conditions (APHIS 1988, 1990). Modifications with broader impact were made in 1993. These provided a more streamlined procedure called “notification” for enabling the field release of transgenic plants not expected to pose serious risks. They also provided a more formal process for applicants to petition the agency for nonregulated status of an engineered plant based on genetic and ecological knowledge of that plant (APHIS 1993). A detailed analysis of APHIS oversight of genetically engineered plants is the focus of Chapters 3, 4, and 5. Chapter 2 provides a more conceptual overview of risk analysis and its application to transgenic plants.