Ortega-Farias, S.O. Servicio Integrado de Agroclimatoligía y Riego (SIAR), Departamento de Producción Agrícola, Facultad de Ciencias Agrarias, Universidad de Talca, Casilla 747, Talca, Chile.A study was performed to evaluate a model for computing net radiation over grass canopies located in Talca (Chile) and Avignon (France). In both locations, an automatic meteorological station was installed over a grass maintained in reference conditions to measure net radiation, solar radiation, air temperature and air vapour pressure on a hourly basis. Results indicated that there was a good correlation between measured (Rno) and estimated (Rne) values of net radiation, with a correlation coefficient greater than 0.95 for both locations. Major disagreements were observed during the night time, but they did not affect the final calculation of net radiation. This analysis suggest that the model could be used in the Penman-Monteith equation to compute crop water requirement in Avignon and Talca, using network measurements for the evaluation of net radiation.