In this study, empirical correlations are developed to estimate the monthly average daily global solar radiation on a horizontal surface (H) for the city of Izmir in Turkey. Experimental data were measured in the Solar-Meteorological Station of the Solar Energy Institute at Ege University. The present models are then compared with the 25 models available in the literature for calculating H based on the main percentage error, root mean error, the main bias error, and correlation coefficient. It can be concluded that the present models predict the values of H for Izmir better than other available models. Copyright (C) 2002 John Wiley Sons, Ltd.