Starch constitutes approximately 75% of the seed on a dry weight basis, which makes this storage polysaccharide a major determinant of yield in many endosperm-based crops. ADPglucose pyrophosphorylase (AGP) catalyzes the first committed step in the biosynthesis of starch and serves as a major flux control point in this pathway. That AGP has such a prominent role in this pathway clearly identifies it as a target for manipulating carbon flux in the seed and potentially yield in higher plants. Knowing that the endogenous AGP enzyme is heat labile, we have developed elite corn lines expressing stability variants of AGP to enhance the agronomic performance of our elite hybrids. A small population of lead events expressing the AGP stability variants has been identified based on molecular and protein data. Initial field data indicates that enhanced stability of AGP may provide enhanced yield under high temperature field conditions. In addition to the yield stability, we have seen favorable changes in other seed attributes. Development of the lead transgenic events and initial field results will be discussed.