Limited water is a primary challenge to high corn yields in North America and most other corn-producing regions of the world.  For that reason, one of Pioneer’s primary goals has been improvement of hybrids for performance in water-limited environments.  Pioneer employs a three-tiered approach to achieve this goal:  continual improvement of Pioneer’s germplasm base and hybrids through conventional breeding, selection and testing; use of new genetic tools and breeding techniques applied to native corn genes (“Drought I” program); and identification and incorporation of transgenic sources of drought tolerance (“Drought II” program).  New products developed from Pioneer’s Drought I program were introduced for the 2011 growing season as Optimum® AQUAmax™ hybrids.  A key aspect of testing these new drought-tolerant products is plant population response.  The objectives of this research study were to evaluate plant populations across hybrids being developed using native drought-tolerance traits (Optimum AQUAmax hybrids) in water-limited environments, understand plant population relationships of hybrids with varying native drought-tolerance and determine economic optimum plant populations for Optimum AQUAmax hybrids.