Glutathione S-transferases (GSTs, EC 2.5.1.18) are a multigene family of detoxification enzymes that biotransform a wide variety of endogenous and exogenous electrophilic substrates, including herbicides. The isozyme GST I from maize exhibits significant catalytic activity for the chloroacetanilide herbicide alachlor and appears to be involved in its detoxifying process. To establish the in planta ability of GST I to detoxify from alachlor, transgenesis studies were carried out. The gene gstI-6His, which encodes for 6His-tagged GST I, was used for the construction of a binary vector suitable for genetic engineering of tobacco plants (Nicotiana tabacum). Through biolistic method transgenic tobacco plants were obtained. Integration of gstI-6His gene in transgenic tobacco plants genome was confirmed by polymerase chain reaction and Southern blot hybridization. The expression of active GST I was established by Western blot analysis, using anti-6His antibody, and by direct purification of 6-His tagged GST I on Ni-NTA agarose. Primary transformed plants harboring the gstI-6His gene were transferred to MS medium supplemented with alachlor and their phenotype was evaluated. The transgenic plants showed substantially higher tolerance to alachlor compared to non-transgenic plants in terms of root, leaves and vigorous development. These transgenic plants are potentially useful biotechnological tools for the development of phytoremediation system for the degradation of herbicide pollutants in agricultural fields.