This chapter was initiated from a symposium and workshop on the scientific advances, issues and bioethics of gene confinement in genetically modified grasses conducted on 13–14 May 2005 at Yale University in New Haven, CT. Genetic modification of dedicated bioenergy crops such as switchgrass will play a major role in crop improvement for a wide range of beneficial traits specific to biofuels. One obstacle that arises regarding transgenic improvement of perennials used for biofuels is the propensity of these plants to be open pollinated, with the undesirable capacity of outcrossing to non-transgenic and wild relative species. We examine previous work on pollen-mediated and seed-mediated gene flow of genetically modified grasses, in particular herbicide resistant traits, relevant to gene flow in grasses providing a perspective on the implementation of this technology for improvement of perennial bioenergy crops.