The herbicide (2,4-dichlorophenoxy)-acetic acid (2,4-D) is considered to be the most cost-effective for eradicating illicit coca plants. Since coca leaves are chewed by the natives of coca producing areas, and, since coca paste and cocaine are widely abused, a study was undertaken to determine whether 2,4-D is translocated into the leaves and transferred to coca paste when coca plants are treated with this herbicide. The study concluded that basal treatment of coca plants with 2,4-D ester resulted in translocation of 2,4-D into the leaves, and this herbicide was detected in high concentrations one week after treatment. Coca paste prepared from leaves obtained from basally treated plants did not contain 2,4-D. Foliage spraying resulted in extremely high concentrations of 2,4-D in the leaves, with significantly high concentrations of the herbicide found one week after spraying. Trace amounts of 2,4-D were detected in coca paste prepared from plants sprayed by the foliage method.