Leaf yellowing and reduced plant density are major problems associated with heat stress injury in cool-season turfgrasses. Our previous research indicates that high temperatures reduce the production of cytokinins, the hormone that controls leaf senescence, tillering and root formation, which are the principal physiological processes underlying this problem. We created two types of transgenic creeping bentgrass with a bacterial gene (ipt) encoding the enzyme adenine isopentenyl phosphotransferase. The ipt gene was ligated to two stress- activated promoters, SAG12 promoter from Arabidopsis that is activated at the start of leaf senescence and HSP18 heat shock promoter that is activated by exposing the plants to temperatures above 35 C. The objectives of this study were to 1) compare the performance of SAG12-ipt and HSP18-ipt transgenic plants to non-transgenic control plants under heat stress, and 2) to examine whether the variance of heat tolerance between transgenic and non-transgenic plants was due to the differences in antioxidant enzyme activities and gene expressions.  Heat stress injury was indicated by turf quality, photochemical efficiency, chlorophyll content and root viability.