Abstract: Radiolabelled glyphosate was used to investigate the effects of organosilicone s urfactants Silwet L-77, Silwet 800, Freeway and Boost on the foliar uptake, tra nslocation and distribution of the formulated glyphosate Roundup? in perennial ryegrass ( Lolium perenne L cv. Grasslan ds Greenstone) over a 72 h time-course. Results indicated that addition of orga nosilicone surfactants significantly decreased the amount of uptake and transloc ation of glyphosate into ryegrass 24 and 72 h after treatment. Four organosilico ne surfactants showed similar antagonism of foliar uptake. The amount of glyphos ate translocation varied according to plant parts, the highest one was in young tissues, and the least one was in leaf 1. Distribution of glyphosate with or wit hout organosilicone surfactants to shoots was much higher than that of to roots 24 and 72 h after treatment. Addition of organosilicone surfactants had no effec t on the distribution rate to shoots and roots.