Four experiments tested a range of doses of the growth-retardant glyphosine on sugar-beet crops between 1970 and 1972. The period of time between application and harvest was varied. One experiment (1972) in nutrient mist culture examined its effect on seedling root development. The growth-retardant decreased root, sugar and top yield of sugar beet at all doses in excess of 0·56 kg a.i. ha^-1 at all treatment times. It increased the α-amino nitrogen content of beet roots significantly (P < 0·05) with doses in excess of 1·12 kg a.i. ha^-1. When applied to the leaves of seedlings with their roots in nutrient mist culture, glyphosine at 500 ppm and 2000 ppm of a.i. in aqueous solution slowed or stopped root elongation.