Moore?s Law has reached the point at which we can build single-chips with multiple processors and significant amounts of memory. Multiprocessor systems-on-chips (MPSoCs) have opened up new application areas, such as low-power and real-time embedded systems. This talk will review the architectures of multiprocessor systems-on-chips and the design methodologies used to create them. MPSoCs make use of advanced processors, memory systems, and on-chip networks, often delivered as intellectual property modules. The design methodologies required to design these complex systems build on earlier VLSI techniques but must address many new problems as well.