A single-chain variable fragment (scFv) antibody specific for the auxinic herbicide, picloram, was expressed in tobacco ('Nicotiana tabacum' L.) to determine if this antibody could attenuate the effects of the herbicide, thereby creating a new mode of developing herbicide resistant crops. Transgenic plants expressing this antibody tolerated picloram doses of 5 g ai ha-1 while wild-type plants died. Translocation of [14C]picloram from the treated leaf to the meristem was reduced in tobacco expressing the anti-picloram antibody, and more [14C]picloram was found in the roots of plants expressing the anti-picloram antibody. No significant metabolism of picloram was observed in either wildtype control plants or plants expressing the anti-picloram antibody. This research indicates that this model system may provide a relatively rapid method of engineering plants for resistance to foliar and soil applied herbicides and environmental contaminants.