fhere is a growing perception that the succesful design and xploitation of complex information systems is critically dependant on: he level of methods and support for performance modelling. Fast: echnological evolution creates a strong demand for analysis: echniques which can handle new hardware and software )rganisations. Performance modelling users are expecting improved: ools in terms of their user friendliness and their integration in the;ystem design and operation process. Providing an image as clear as possible of the recent advances in: hese areas is the objective of the serie of In t ern a t ion a 1 Conference on Modelling Techniques and Tools for Computer Performance Evaluation. We believe thst the 4th edition does respond to the objective. It illustrates the most recent trends in our jomain and gives insight into what we may expect in terms of new modelling techniques; tools and practices in the future years. The proceedings include the twenty seven papers accepted by the Program Committee (but of sixty six submitted) and three invited papers presented at the Conference. They cover the following topics: * Modelling Tools * Networking * Architecture and Workload * Protocols * Architecture Configuration * Parallelism ix * Performability * Algorithms We would like to express our sincere apprecIatIOn and gratitude to the members of the Program Committee and to the reviewers for their time and effort. Without their kind cooperation, the Conference would not have been possible.