Abstract: The research has been undertaken to compare the daily reference alfalfa evapotranspiration (ET) value measured by Penman-Monteith method with those determined by the Penman, Adjusted Penman and Jensen methods. Estimation of reference ET has been calculated using 5 years data of Southwest Research Extension Center of Kansas State University (KSU), USA at Garden city kept recorded at KSU Weather Data Library. The comparison of the four methods includes daily peak ET values determined by the methods under study, correlation of the major meteorological data with the ET values, average and total ET values and regression equations with reference to the Penman-Monteith method. The estimation made by the Penman-Monteith method shows the best reflection of the climatic data in comparison to those of the other methods in terms of correlation with climatic parameters.