The innovative progress in the development of parallel computing systems and their increasing availability have caused a rise in interest in the scientific principles that underlie parallel computation and parallel programming. The biannual Parallel Architectures and Languages Europe (PARLE) conferences aim to present current research on all aspects of the theory, design and application of parallel computing systems and parallel processing. This volume, offering the results of PARLE '91, has been broadened in scope in order to cover the area of parallel algorithms and complexity, in addition to the central themes of parallel architectures and languages.