Roundup Ready® crops provide growers greater flexibility in weed management due to the ability of glyphosate to control larger weeds than other herbicides. Although this is advantageous, it can lead to yield losses if the glyphosate application is delayed too long. Another concern is the risk of selecting glyphosate-resistant weeds due to extensive use of glyphosate. Research was conducted to determine the value of preemergence herbicides in protecting crop yields and reducing selection pressure in Roundup Ready® corn and soybeans.