Information regarding gene flow in wind-pollinated outcrossing forage and turf grasses is essential for regulation and future releases of transgenic cultivars. Two independent experiments are being undertaken: pollen dispersal of tall fescue and Italian ryegrass, and hybridization potential between different grass species. Both experiments use transgenic tall fescue carrying marker genes, transgenic Italian ryegrass with down-regulated pollen allergen and transgenic Italian ryegrass carrying a marker gene, as the source of pollen. The pollen dispersal experiment used transgenic plants in a central plot, surrounded by exclosures containing recipient plants of the same genotype for each of the two test species. A total of 360 transgenic tall fescue and 360 each of the two transgenic ryegrass lines were used as pollen donors in the central plot. Wild-type tall fescue and Italian ryegrass were used as the recipients and grown in exclosures, with 4 plants from each species in one exclosure. The exclosures were 25 m apart and aligned in eight directions, up to a distance of 400 m from the central source plants. The experiment on hybridization potential was designed to investigate crossability between tall fescue, Italian ryegrass and 9 related species of Festuca and Lolium. A large number of samples will be analyzed for progenies collected from the experiments in the summer of 2005. The distance and frequency of pollen flow, the probability/frequency of cross hybridization and the effects of down-regulation of a major pollen allergen on pollen dispersal will be investigated.