High groundwater pumping costs and rapidly declining water levels in the Texas High Plains makes it imperative to improve irrigation water management for sustainability and regional economic viability. In this area, agriculture uses approximately 89% of groundwater withdrawals. Accurate regional evapotranspiration (ET) maps would provide valuable information on crop water use, irrigation efficiencies and aid in estimating important regional hydrology (e.g., recharge, groundwater pumping, etc.). In this study, an Aerodynamic Temperature-based Surface Energy Balance Model for estimating spatially distributed ET rates was evaluated. Data from four precise large-scale monolithic weighing lysimeters (two with irrigated crops and two with dryland crops) at the Conservation and Production Research Laboratory, USDA-ARS at Bushland, TX [35 deg 11' N, 102 deg 06' W; 1,170 m elevation MSL] were used to evaluate the model. For this purpose, a Landsat 5 Thematic Mapper image was acquired on 23 July 2006, for the overpass at 17:19 GMT. The satellite image covered a major portion of the Southern High Plains (parts of the Texas Panhandle and northeastern New Mexico). Lysimeter-measured ET rates varied from 2.4 to 7.8 mm/d. Good agreement was found between remote sensing ET estimates and lysimeter derived ET values. The model's strength and weaknesses, under the climatic conditions encountered in the Texas High Plains, will be discussed and summarized.