Cotton plants were treated with C14-ring-labeled 2-methylmercapto-4,6-bis(isopropylamino)-s-triazine (prometryne) which was soil-incorporated or placed in solution cultures. C14-labeled material accumulated in the lysigenous glands of roots, stems and leaves. No evolution of C14-carbon dioxide could be detected. Unaltered C14-prometryne was present in stems and leaves 23 weeks after treatment, but no radioactive materials could be detected in the seed. Small amounts of hydroxypropazine were isolated from the stems and leaves of plants grown in soil, but none was detected in plants grown in solution culture. Both water-soluble and acetone-insoluble radioactive materials accumulated in the leaves, stems and roots of all treated plants.