1. 2,4-Dichlorophenoxyacetic acid was effective as a differential herbicide when applied as an aqueous spray in concentrations of from 250 to 1000 p.p.m. or more. 2. Plants killed by these sprays were dandelion, narrow-leaf plantain, Dutch white clover, chickweed, pigweed, woodsorrel, knotweed, broad-leaf dock, bind-weed, and shiny pennywort. Other plants, such as broad-leaf plantain, sheep sorrel, daisy, yarrow, and various species of Rubus, were relatively insensitive to the acid. 3. Two applications of either 500 or 1000 p.p.m. concentration of the acid in aqueous solution were made to well-established Kentucky bluegrass sod without apparent injury to the grass. In addition, Kentucky bluegrass seed planted under a light top dressing of soil, which was then sprayed with the acid concentrations, germinated and readily became established in these lawn areas. 4. It was possible to obtain 95% control of dandelion and narrow-leaf plantain by a single spray application of a solution containing 1000 p.p.m. of ...