All economically important Brassica species have been successfully transformed using Agrobacterium tumefaciens. Although different tissues have been used as explants, hypocotyls remain the most desirable explants for Brassica tissue culture owing to their amenability to regeneration. Young explants excised from 3- to 4-d-old seedlings have exhibited optimal regeneration potential; the addition of adjuvants such as silver nitrate to the selection medium is necessary to achieve high efficiency of transformation. This chapter describes an Agrobacterium-mediated transformation protocol for Indian mustard based on inoculation of hypocotyls. The selectable marker gene used encodes for neomycin phosphotransferase II (nptII), and the selection agent is kanamycin.