In this study, daily global radiation for Toledo (39degrees53'05"N. 4degrees02'58''W. Spain) were utilized to determine monthly-specific equations for estimating global solar radiation from sunshine hours and to obtain improved fits to monthly Angstrom-Prescott's coefficients. Models were compared using the root mean square error (RMSE), the mean bias error (MBE) and the t-statistic. According to our results, all the models fitted the data adequately and can be used to estimate the specific monthly global solar radiation. Average RMSE and MBE for comparison between observed and estimated global radiation were 1.260 and -0.002 MJ m(-2) day(-1), respectively. The t-statistic was used as the best indicator, this indicator depends on both, and is more effective for determining the model performance. The agreement between the estimated and the measured data were remarkable and the method was recommended for use in Toledo (Spain). (C) 2004 Elsevier Ltd. All rights reserved.