This paper presents a wavelet neural-network for learning and approximation pf chaotic time series. Wavelet networks are a class of neural network that take advantage of good localization and approximation properties of multiresolution analysis. These networks use wavelets as activation fynction in the hidden layer and a hierarchical method is used for learning. Comparisons are made between a wavelet network tested with two different wavelets, and the typical feedforward network trained with the back-propagation algorithm. The results reported in this paper show that wavelet networks have better approximation properties than back-propagation networks.