Gene flow is not unique to genetically modified (GM) crops, but the possibility of the spread of transgenic DNA to wild and domesticated relatives raises a new set of issues for scientists and policymakers to consider. Unfortunately, we are still too often unable to quantify the risks of ecological damage associated with gene flow. This is due partly to the huge breadth of knowledge required to assemble a comprehensive risk assessment. For example, many scientists active in research on the mechanics of gene flow nevertheless lack a deep understanding of what is required to identify, characterise and assess ecological risk, and many of those who are aware of the risk assessment process and the framework used for legislation have insufficient knowledge of the reproductive biology, agricultural systems, modelling, and ecological literature required to compile a balanced risk assessment. This book, set in the context of gene flow in general, considers the assessment, measurement, and management of the risks of gene flow from GM plants, combining the expertise of all the various stakeholders. It is directed at researchers and professionals in plant molecular genetics and plant ecology, in both the academic and industrial sectors.