Abstract: This study was carried out in the summer of 2001 in a 3 year old and in the summer of 2002 in a 4 year old sweet cherry trees (Prunus avium, variety Z-900) on Mazzard rootstocks in Bayramic-Canakkale which is located in the west part of Turkey. Micro-sprinkler irrigation was selected as the irrigation method. The trees were subjected to four micro-sprinkler irrigation treatments (T-1, T-2, T-3 and T-4). The water applied in treatment T-3 was considered sufficient to satisfy fully needs of the crop (100% of ETc) and to allow good rooting and tree growth. The water balance relationship was used in estimating ETc. A total of 4 climatological methods were selected for estimating reference crop evapotranspiration on a daily basis. Some of these methods are based on combination theory and others are empirical methods based primarily on solar radiation, temperature ans relative humidity. An attempt was made in the current study to develop regional relationship between the evapotranspiration measured and that estimated by the climatological methods, such as FAO-Penman, Penman-Monteith, FAO-Radiation and FAO-Blaney-Criddle. Performance of the climatological methods in estimating the ETo values as compared to the measured values was evaluated on the basis of root mean square error (RMSE). In 2001, the Penman-Monteith equation gave the best results followed by FAO-Penman, FAO-Radiation and FAO-Blaney-Criddle. In 2002, the Penman-Monteith and FAO-Blaney-Criddle equations gave same results.