Genetically engineered cotton (Gossypium hirsutum) varieties that are resistant to certain herbicides or insects are fast becoming an important asset to producers. While it is well documented how these varieties respond to herbicide applications and insect attacks, their response to plant growth regulators (PGRs) is unknown. A study was conducted in 1997 to address this question. Cotton varietes DPL 5690 Roundup Ready^®, Stoneville BXN 47 Buctril^® resistant, DPL 33B, DPL 5409, TAMCOT Sphinx, and DPL 50 were evaluated in this test. The PGR programs utilized are detailed in Table 1. Lint yields between the varieties were different with BXN 47 yielding the most (Table 2). This difference is primarily attributed to increased ginout percentage. All varieties responded similarly to the PGR programs. Any treatment containing mepiquat chloride (MC) significantly reduced plant heights compared to the control. The PGRs did not influence boll numbers or distribution. Lint yields were not significantly increased with any PGR program. The MEPRT treatment increased seed size compared to the control.