This letter is to inform you of the results of a recently conducted acute oral toxicity study (LD50) in rats with a R&D proprietary mixture containing these materials. Groups of 5 male and 5 female Crl:CD-BR rats were fasted overnight and then administered the test mixture by intragastric intubation. After dosing, the rats were observed for mortality and clinical signs of toxicity over a 14-day observation period. The R&D proprietary mixture contained 2,4-D and Metsulfuron Methyl. The rats were dosed at 500, 720, or 1037 mg/kg. Mortality occurred in 0/10, 7/10, and 9/10 rats dosed at 500, 720, and 1037 mg/kg, respectively. Hypoactivity and ataxia were observed in surviving male and female rats dose at 500 or 720 mg/kg. Additionally, hypoactivity and ataxia were observed from the day of dosing through 4 days after dosing in one male rat dosed at 1037 mg/kg. This rat was found dead 5 days after dosing. The LD50 was calculated to be 705 mg/kg.