Gene flow from transgenic glyphosate-resistant crops can result in the adventitious presence of the transgene, which may negatively impact markets.  Gene flow can also produce glyphosate-resistant plants that may interfere with weed management systems.  The objective of this article is to review the gene flow literature as it pertains to glyphosate-resistant crops.  Gene flow is a natural phenomenon not unique to transgenic crops and can occur via pollen, seed and, in some cases, vegetative propagules.  Gene flow via pollen can occur in all crops, even those that are considered to be self-pollinated, because all have low levels of outcrossing.  Gene flow via seed or vegetative propagules occurs when they are moved naturally or by humans during crop production and commercialization.  There are many factors that influence gene flow; therefore, it is difficult to prevent or predict.  Gene flow via pollen and seed from glyphosate-resistant canola and creeping bentgrass fields has been documented.  The adventitious presence of the transgene responsible for glyphosate resistance has been found in commercial seed lots of canola, corn and soybeans.  In general, the glyphosate-resistant trait is not considered to provide an ecological advantage.  However, regulators should consider the examples of gene flow from glyphosate-resistant crops when formulating rules for the release of crops with traits that could negatively impact the environment or human health.