Some factors affecting the absorption and translocation of radioactive 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in blackjack oak (Quercus marilandica Muench.) were studied. Absorption of 2,4,5-T was less in plants treated late in the growing season than in those treated earlier. Absorption and translocation of 2,4,5-T were inversely related to soil moisture stress. Increases in the rate of application from 10 to 50 μg of 2,4,5-T per plant caused a decrease in absorption and translocation, but decrease of the latter did not occur until the rate was increased above 25 μg/plant. Translocation was highest in June and was higher from the leaves of mature plants than from young regrowth.