Studies were conducted at the University of Arkansas Northeast Research and Extension Center at Keiser Arkansas and at the University of Missouri Delta Center at Portageville Missouri to evaluate the effect of glyphosate on Roundup Ready® cotton. Eleven Roundup Ready® cotton varieties common to both the north Arkansas and southeast Missouri official variety test (OVT) were selected for the evaluation and planted during the 2001 growing season. The test at Keiser was a split plot with varieties receiving glyphosate applications and varieties receiving no glyphosate. The Missouri test was a traditional variety test with all varieties receiving an over-the-top and a post direct application of glyphosate. Both tests were irrigated and arranged as a randomized complete block with 4 replication. All other production practices were based on university recommendations for optimal cotton production in the respective locations. There was no significant variety by glyphosate interaction in the Arkansas test and yields followed similar trends as the Missouri test. In both tests, variety had a significant effect on yield and fiber data. These data suggest that Roundup Ready® cotton cultivars can be accurately evaluated in conventional variety testing programs. The application of glyphosate did not effect the yield or fiber properties of any variety tested in this test.