A new method for estimation of regional evapotranspiration using satellite derived datais proposed. This method estimates daily regional evapotranspiration by combining high resolution LANDSAT-TM data, NOAA-AVHRR data of which the estimation accuracy of surface temperature is high, and wide-area representative radiosonde data. As a case study, we caluculated the epavotranspiration for 2 districts in the Hokkaido Ishikari Plain using this method. Results are reasonable. Though there is no direct method for verification, comparison with the Prisetley-Taylor method shows that the results correctly reflect the effects of land use. This result shows that this method is sensitive to land use and that it is a useful method for estimation of the regional evapotranspiration. The representativeness of the radiosonde data is questionable in the comparison between results from 2 regions. Though there are some details to be improved, this could be a valuable method by which the regional evapotranspiration can be estimated using easily obtainable data. © 2000, The Society of Agricultural Meteorology of Japan. All rights reserved.