Absorption and translocation of the 14C-labeled herbicide 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione (bioxone) in cotton (Gossypium hirsutum L. ‘Acala 4-42-77′) were studied using autoradiography and counting. Foliar penetration and acropetal distribution of 14C occurred within 3 hr and increased with time. No basipetal translocation of 14C out of treated leaves was detected 6 days after treatment. Radioactivity first occurred in the leaf veins, then more generally in interveinal tissues distally from the point of application. Absorption into roots of 30-day-old plants via nutrient solution was rapid; translocation into stem and leaves occurred 12 to 24 hr after treatment. Translocation of 14C was more rapid in 40-day plants. Radioactivity in leaves of root-treated plants was first located in the veins, then distributed throughout with accumulation of 14C in lysigenous glands and leaf margins. Little 14C moved into young growing points; most accumulated in older leaves. Plants treated with heterocyclic ring-labeled and phenyl ring-labeled bioxone-14C had similar distribution patterns of 14C, characteristic of compounds which move only in the apoplast.