The genetic transformation of opium poppy, Papaver somniferum, offers the opportunity to study the mechanisms involved in the regulation of benzylisoquinoline and morphinan alkaloid biosynthesis. The development of an efficient transformation protocol for opium poppy has allowed us to transform a range of genotypes from all around the world, including previously recalcitrant high-yielding commercial Australian cultivars. The method involves Agrobacterium tumefaciens infection of hypocotyl explants, followed by the production of antibiotic or herbicide resistant embryogenic callus, the subsequent induction of somatic embryos and development into normal plants. The use of different selective agents, binary vectors, and poppy genotypes has demonstrated the robustness and reliability of this protocol in the production of many hundreds of confirmed transgenic poppies.