This chapter describes an Agrobacterium tumefaciens -mediated transformation protocol for torenia, a plant that has several useful characteristics and is primarily used for ornamental and experimental purposes. Leaf segments of torenia were co-cultured with A. tumefaciens containing a vector plasmid for 7 days at 22�C under dark conditions on Murashige and Skoog (MS) medium containing 1 mg/L benzyladenine, 1 mg/L indoleacetic acid, and 100 μM acetosyringone. Subsequent culturing at 25�C under a 16-h photoperiod with fluorescent light on MS medium containing 1 mg/L benzyladenine, 300 mg/L carbenicillin, and selection agent (300 mg/L kanamycin or 20 mg/L hygromycin) allowed for transformant selection. Transgenic shoots were obtained from green compact calli after 2–3 months of culture in the selection medium. This method can achieve a transformation rate of approximately 5% (transformants/explant).