Technical Abstract: One major challenge to producing runner market type peanuts in west Texas is the potential for early frost and poor crop maturity that could result in flavor problems. Prohexadione calcium is a plant growth regulator that inhibits the synthesis of gibberellic acid in peanut resulting in reduced vine growth with the potential to shift resources toward pod production. This product is labeled for reducing vine growth in order to improve row visibility. Reducing vine growth for row visibility is not an issue in west Texas making the recommended rate and timing not applicable for the objectives of this research. A field study was conducted in 2005, 2006, and 2007 to determine if prohexadione calcium positively affects peanut maturity, yield, and biomass partitioning. Prohexadione calcium was applied at first row closure and two weeks after row closure at all combinations of 0, 0.25, and 0.5 kg/ha for a total of seven treatments. Applications were made with a CO2 backpack sprayer. Plots were established in a grower’s field under irrigation and were harvested with research equipment. Crop growth habits, pod yield, grade, maturity, and sensory data will be reported.