Book excerpt: This volume includes very high quality papers in different areas of computer and information sciences. The main themes are (computer network) performance evaluation and artificial neural networks and their applications. The latest developments in these areas are presented by a number of distinguished researchers from all over the world. These proceedings of The 13th International Symposium on Computer and Information Sciences (ISCIS'98) contain outstanding papers specifically related to the areas of "Gelenbe" neural networks and their applications, performance of computer-communication networks, simulations and analytic methods in order to study the performance of telecommunication networks, scheduling and resource allocation in computer and multimedia systems, stochastic ordering applied to performance evaluation, and simulation of virtual humans.