Previous research has shown that glyphosate added to Roundup Ready cotton after the fifth true leaf stage may affect overall yield of cotton. In 2006, Roundup Ready Flex will be released to combat these limitations. With this new technology, producers will have a wider window of application time for season long weed control. Experiments were conducted at the Black Belt Branch Experiment Station in Brooksville, MS, the Plant Science Research Center at Mississippi State Universtiy, Macobson Farms in Greenwood, Ms, and the Monsanto Delta Research Station in Leland, MS. These experiments were conducted to determine the effects of glyphosate on traditional Roundup Ready Cotton and several varieties of Roundup Ready Flex Cotton applied at 1x and 2x rates throughout the growing season. Both traditional Roundup Ready and Roundup ready Flex were treated with an in-season maximum load of glyphosate. Applications were made at the specific node intervals with a 2-row backpack sprayer. Box mapping will then be used to determine the effects of the glyphosate applications on boll retention, square abscission, delayed maturity, and subsequent yield loss.