With increasing cotton (Gossypium hirsutum L.) seed costs, determining optimum plant populations is increasingly important. The optimum plant population is impacted by planting date as it affects seasonal heat units, and thus the potential for yield compensation in reduced populations. In 2005 and 2006, field experiments were conducted to evaluate the impact that plant population and planting date has on mepiquat chloride (Mepex) application timing and rate. These experiments were conducted at the Virginia Tech Tidewater Agricultural Research and Extension Center in Suffolk, Virginia, the North Carolina State University Peanut Belt Research Station in Lewiston, North Carolina, and the Louisiana State University Dean Lee Research Station in Alexandria, Louisiana. In order to achieve various plant populations, cotton was planted at 1.5, 3.0, and 5.0 seeds per foot of row. These populations were applied to two planting dates, which were managed separately and included an early planting in late April, followed by a late planting 21 days later. The Mepex application timing and rate was determined based on the modified early bloom strategy (MEB), which utilizes moisture conditions, plant height, height to node ratio, and internode length measurements to aid in decision making. These measurements were collected and analyzed at 10-14 days after first-square, early bloom, and 10-14 days after early bloom, with Mepex applications made based on the guidelines within the 2005 and 2006 Virginia Cotton Production Guides. All treatments were evaluated on control of plant growth, maturity, and boll retention based on measurements taken by the MEB strategy guidelines and plant mapping. Plant height, nodes above white flower, plant mapping, maturity, and yield data from both years and all locations will be combined and analyzed for reporting.