Quantification of evapotranspiration (ET) requires understanding of the capabilities and limitations of each technique. This symposium is focused on the accuracy, uncertainty, and limitations of established techniques for measuring or modeling ET. We invite presentations on the theoretical and empirical considerations that affect the accuracy of various ET measurement or modeling techniques. Techniques may include eddy correlation, Bowen ratio energy balance, lysimetry, surface renewal, water balance, sap flow, scintillometry, remote sensing-based algorithms, and direct modeling. A keynote speaker will be featured, but contributed presentations are also included. The symposium will conclude with a panel discussion.