Since their introduction in 1996, glyphosate-tolerant crops have been widely adopted in the United States. The adoption of the glyphosate-tolerant cropping system and the increasing use of glyphosate have contributed to the development of glyphosate-resistant weeds and the increased prevalence of hard-to-control weeds. Dow AgroSciences is developing the Enlist Weed Control System to address this problem. This herbicide-tolerant trait technology provides robust tolerance to 2,4-dichlorophenoxyacetic acid (2,4-D) in corn, soybeans, and cotton. It will be combined with other traits that provide glyphosate tolerance. Concurrent with the development of the trait technology, Dow AgroSciences is developing new 2,4-D-based products to be used in this weed control system. Enlist Duo herbicide (PremixED), a premix formulation that combines 2,4-D choline salt with glyphosate, employs novel formulation technology that substantially reduces the potential for off-target movement through ultralow volatility and minimized potential for spray droplet drift. PremixED also provides greater spray tank stability and compatibility than current tank mixes of 2,4-D with glyphosate. The herbicidal efficacy of the new formulation is comparable to that of an equivalent tank mixture.