This work presents the results of applying different automatic learning techniques to the calculation of daily ultraviolet radiation from daily global radiation on a horizontal surface. Using the data from three Spanish locations, a zonal study was made, which was finally combined in models for general application. Using the corresponding atmospheric transparency index, three models based on multivariate linear regression, non-linear regression and generation of fuzzy inference systems, respectively, were designed. The results obtained verify the good behavior of the fuzzy inference system calculated. (C) 2003 Elsevier Ltd. All rights reserved.