Amine salts of 2,4,5-trichlorophenoxy-propionic acid (silvex) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were applied to tall larkspur, Delphinium barbeyi Huth, at 2, 4, and 8 lb/A on three dates. Leaf and stem samples collected 1, 2, and 3 weeks after treatment yielded significantly higher concentrations of alkaloids than did controls. Leaves and stems from plants treated with silvex contained more alkaloids than did those treated with 2,4,5-T. Alkaloid concentration in the leaves varied directly with the rate of herbicide following the first treatment in mid-July, but this relation was not apparent in samples obtained from the third treatment in August.