Technical Abstract: Surface energy fluxes and evapotranspiration (ET) have long been recognized as playing an important role in determining exchanges of energy and mass between the hydrosphere, atmosphere, and biosphere. In this study, we applied the METRIC (Mapping ET at high Resolutions with Internal Calibration) algorithm on a Landsat Thematic Mapper (TM) image acquired on July 10, 2007, to derive hourly surface energy fluxes and ET for the highly advective Texas High Plains. Performance of the METRIC algorithm was evaluated by comparing estimated surface temperature, net radiation, soil heat flux, and hourly ET measured on four large lysimeters in Bushland, Texas [350 11' N, 1020 06' W; 1,170 m elevation MSL]. Agreements between predicted and measured values of both surface temperature and net radiation were excellent. Comparison of METRIC-estimated instantaneous ET values with lysimetric measurements indicated that METRICTM may provide good ET estimates for both irrigated and dryland fields. However, relatively large errors in predicting ET for lysimeter fields under dryland management may be due to errors in the selection of the hot pixel.