Jimsonweed (Datura stromonium) was treated with carboxyl-labeled C14 2,4-dichlorophenoxyacetic acid (2,4-D*); auto-radiographs and extraction of radioactive materials were used to determine the movement and form of the herbicide. Activity rapidly decreased in the leafy tissue. There was an accumulation of activity in the stem, but very little accumulation in the roots. With the exception of the stem tissue where minor alteration of the herbicide occurred, 2,4-D* was the only radioactive material recovered from jimsonweed. A loss of radioactivity from the root systems indicated a possible detoxification mechanism for jimsonweed. Up to 25% of the 2,4-D* applied to jimsonweed was expelled from the roots in six weeks.