Simazin, 2–chloro–4,6–bis(ethylamino)–s–triazine, is a relatively new herbicide that has shown much promise for pre-emergence weed control in corn (3,4,7). It is a white crystalline compound with a solubility of 5 ppm in water and 900 ppm in chloroform. This compound is non-flammable, non-corrosive, and has an acute oral toxicity greater than 5 g/kg for mice. Simazin is said to be highly toxic to cucumber, of intermediate toxicity to cotton, and non-toxic to corn. Schneider (6) reported it to be effective only when absorbed through the root system. This study was begun to determine whether the differences in susceptibility of these plants and the limitation of effectiveness of simazin to the root system could be correlated with its absorption and translocation.