Field experiments involving novel transgenic plants are regulated by federal and state agencies as well as Institutional Biosafety Committees. Transgenic plants that produce industrial or pharmaceutical products are regulated more stringently than others, as are species that outcross and those that can interbreed with wild relatives. This talk provides an overview of gene flow and its ecological, evolutionary, and economic consequences in agricultural landscapes. In sunflower, for example, recent research has enhanced our understanding of the extent of pollen- and seed-mediated gene flow from cultivated plants. Field tests of transgenic sunflower plants have included open-air plots of male-sterile plants and caged plots into which pollinating bees were introduced. Despite a wealth of information about how to grow transgenic sunflowers safely in small field plots, the Institutional Biosafety Committee at a state university recently refused to authorize this type of research. The blocked application received an unusual amount of scrutiny, perhaps because of concerns that a transgene for enhanced rubber production might spread to wild sunflowers. I will discuss the types of problems that can arise if experimental transgenes “escape” from field test sites and persist in wild or cultivated gene pools of common crops. This is most likely to occur when the source plots are very large relative to recipient populations, as occurred in creeping bentgrass grown in Oregon. Human error can also play a role when required procedures are not followed. Researchers who plan to grow transgenic plants to reproductive maturity can benefit by being aware of the ecology of gene flow as well as regulatory hurdles that can slow the progress of their research.