We studied the uptake and transport of 4-amino-3,5,6-trichloropicolinic acid (picloram) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) alone and in combination and in the presence of 1,1′-dimethyl-4,4′-bipyridinium salt (paraquat) by honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell), huisache (Acacia farnesiana L. Willd., yaupon (Ilex vomitoria Ait.), and bean (Phaseolus vulgaris L.). Paraquat reduced transport of picloram by mesquite, huisache, and bean. Paraquat increased uptake of picloram by yaupon but did not affect transport. The uptake and transport of 2,4,5-T by mesquite decreased in the presence of picloram, but the uptake and transport of picloram increased in the presence of 2,4,5-T. Increasing ratios of 2,4,5-T:picloram up to 16:1 continued to increased uptake and transport of picloram; the inverse effect occurred for 2,4,5-T when picloram:2,4,5-T ratios were increased.