Cotyledon explants of Ipomoea trichocarpa E11, were inoculated with ten strains of Agrobacterium rhizogenes. Hairy roots were produced from the cut surface of explants by inoculation with all bacterial strains. No clear differences in rhizogenicity were observed among the bacterial strains of A. rhizogenes tested. Whole plants were regenerated from the hairy roots transformed by all of the bacterial strains. These hairy root-derived plants exhibited the expected transformed phenotype, which was sexually transmitted to the progenies in Mendelian fashion as a single dominant locus. Transgenic I. trichocarpa plants possessing both the npt II and gus genes were also obtained from the hairy roots by infection with Agrobacterium rhizogenes containing the binary vector pBI121 in addition to the wild-type Ri-plasmid.