A study was conducted to examine the effect of ammonium sulfate (AMS) applied with and without surfactants (Induce, Silwet L-77 and Methylated seed oil) on the efficacy of glyphosate. Herbicide treatments were applied to broadleaf weeds–Brazil pusley (Richardia brasiliensis), Spanish needles (Bidens pilosa), Florida beggarweed (Desmodium tortuosum) and Pigweed (Amaranthus retroflexus) and grassy weeds–Guineagrass (Panicum maximum), Johnsongrass (Sorghum halepense) and Crowfoot grass (Dactyloctenium aegyptium). The per cent control of both weed types was significantly higher with the application of AMS or the surfactant individually, or the surfactant plus AMS to glyphosate at 370 g/ha over no surfactant or AMS. Per cent control of grass weeds was 100 with the addition of any one of the surfactant except with glyphosate+L-77, where per cent control of Guinea grass and Johnson grass was only 82 and 85, respectively, two weeks after treatment (WAT). Per cent control of Brazil pusley and Spanish needles with glyphosate at 370 g/ha was low (20-38) 1 WAT. Addition of AMS improved efficacy of glyphosate in Brazil pusley 1 and 2 WAT. This effect, however, could not be observed 3 WAT. Effect of addition of AMS was apparent in Spanish needles and Florida beggarweed 2 WAT. Glyphosate alone, however, provided 93-100% control of Spanish needles, Florida beggarweed and pigweed 3 WAT. Per cent control of grassy weeds was complete 2 WAT with glyphosate at 370 g/ha with or without surfactants except with L-77 where it showed antagonistic effect.