Roundup Ready crops have become very popular in the short time that this technology has existed. In particular, Roundup Ready soybeans accounted for 75% of U.S. soybean acres in 2002 and the percentage in Wisconsin is likely higher. Adoption of Roundup Ready corn has been slower because of several factors such as international marketing and the potential that the weed management system is not as simple as in soybeans. Because glyphosate (e.g., Roundup, Touchdown, etc.) lacks residual activity, it is logical to presume that a residual herbicide either applied at planting or tank mixed with the glyphosate may improve weed control in both Roundup Ready soybeans and corn. However, this residual herbicide would add cost for the product and possibly for an added application. Does the weed control and associated yield differ enough to justify this expense?