Perennial ryegrass (Lolium perenne L.) is the most widely distributed grass species in areas with temperate climate. Genetic engineering of perennial ryegrass is complementing traditional breeding in the development of improved germplasm. The generation of large numbers of transgenic perennial ryegrass plants from turf type- or forage type cultivars following biolistic or Agrobacterium-mediated gene transfer was recently reported by us. Transgenic plants generated by the two alternative transformation systems were compared regarding transgene integration pattern, fertility and stability of transgene expression after vegetative and sexual reproduction. Advantages and limitations of the two perennial ryegrass transformation systems are discussed.