Absorption and translocation of the growth regulator 14C-chlorflurenol (methyl-2-chloro-9-hydroxyfluorene-9-carboxylate) and of the herbicide 14C-dicamba (3,6-dichloro-o-anisic acid) were studied in Canada thistle [Cirsium arvense (L.) Scop.]. Also investigated was how foliar treatments with chlorflurenol affected leaf uptake and distribution of dicamba by Canada thistle. Plants were grown in aerated nutrient solution. 14C-chlorflurenol showed strong acropetal and weak basipetal movement. Thirty-two percent of the foliar applied 14C-dicamba was absorbed and most of the radioactivity tended to accumulate in the young growing leaves. Only 0.6% of the applied radioactivity moved to the roots. Leaf absorption and basipetal translocation of 14C-dicamba were increased two- and ten-fold, respectively, by the simultaneous addition of chlorflurenol at 0.6 kg/ha. Root bud activity was increased when 4-week-old Canada thistle plants were foliarly treated with chlorflurenol at 0.6 kg/ha. Field work demonstrated that Canada thistle control could be enhanced by chlorflurenol addition to dicamba.