The design of multiprocessor architectures differs from uniprocessor systems in that the number of processors and their interconnection must be considered. This leads to an enormous increase in the design-space exploration time, which is exponential in the total number of system components. The methodology proposed here, called <italic>Intelligent Concurrent Object-Oriented Synthesis</italic> (ICOS) methodology, makes feasible the synthesis of complex multiprocessor systems through the application of several techiques that speed up the design process. ICOS is based on <italic>Performance Synthesis Methodology</italic> (PSM), a recently proposed object-oriented system-level design methodology. Four major techniques: object-oriented design, fuzzy design-space exploration, concurrent design, and intelligent reuse of complete subsystems are integrated in ICOS. First, object-oriented modeling and design, through the use of object-oriented relationships and operators, make the whole design process manageable and maintainable in ICOS. Second, fuzzy comparison applied to the specializations or instances of components reduces the exponential growth of design-space exploration in ICOS. Third, independent components from different design alternatives are synthesized in parallel; this design concurrency shortens the overall design time. Lastly, the resynthesis of complete subsystems can be avoided through the application of learning, thus making the methodology intelligent enough to reuse previous design configurations. Experiments show that all these applied techniques contribute to the synthesis efficiency and the degree of automation in ICOS.