Zenith radiance was measured in Pamplona (Spain) during sixteen months under different sky conditions. 5th degree polynomials that relate log(L(z)) with solar elevation return the best correlations both when considering the entire dataset as well as when data are split into the five sky conditions considered. Besides, we have obtained simple relations, with high correlation coefficients and low Relative Root Mean Square Difference, to predict the values of the mean zenith radiance for a type of sky from the mean zenith radiance values of one or more of the remaining four types. Lastly, we obtained month-hour equal mean zenith radiance contours for each of the five sky types considered in the study as well as for all the skies as a whole. (C) 2009 Elsevier Ltd. All rights reserved.