Two techniques for extrapolating detailed micrometeorological or lysimetrical measurements of evapotranspiration to field other than intensely instrumented experimental sites are presented and discussed. The first approach utilizes net radiation, air temperature, vapor pressure and wind speed data and crop resistance in the calculations. Both techniques are dependent on the availability of a relationship between air resistance and windspeed. With remotely sensed surface temperature, the need for the difficult-to-get crop resistance data is eliminated. The results of the first techniques are demonstrated to compare favorably with evapotranspiration calculated from the energy balance data. The evapotranspiration from field plots of cotton stressed to different degrees is calculated from remotely sensed surface temperatures. For this particular crop it appears that, where the leaf water potential is -20 bar, evapotranspiration is about equal to the intercepted net radiation. At lower leaf water potential, evapotranspiration was lower than the intercepted net radiation. * Contribution of the Texas Agricultural Experiment Station.