Six parental giant bermudagrass [Cynodon dactylon (L.) Pers. var. Aridus Harlan et de Wet] clones and their F1 progenies from 27 crosses out of a possible 30, were evaluated for their responses to two concentrations [5 and 10 p/m weight per volume (w/v)] of Ametryne [2-(ethylamino)- 4(esopropylamino)-6-(methylthio)-s-triazine]. There were significant differences among parents and progenies at 10 but not at 5 p/m Ametryne. Tolerant parents had more tolerant progenies than did susceptible parents, indicating that tolerance may be a heritable trait. Progenies had tolerance ratings consistently lower than midparent values, suggesting that susceptibility is partially dominant. General combining ability, but not specific combining ability, was significant for the 10 p/m test, suggesting that breeding programs for tolerance to Ametryne should proceed in terms of additive genes. Crosses of tolerant parents should be expected to produce a high proportion of tolerant progeny.