Dynamic voltage scaling (DVS) circuits have been widely adopted in many computing systems to provide tradeoff between performance and power consumption. The effective use of energy could not only extend operation duration for hand-held devices but also cut down power bills of server systems. Moreover, while many chip makers are releasing multi-core chips and multiprocessor system-on-a-chips (SoCs), multiprocessor platforms for different applications become even more popular. Multiprocessor platforms could improve the system performance and accommodate the growing demand of computing power and the variety of application functionality. This paper summarizes our work on several important issues in energy-efficient scheduling for real-time tasks in multiprocessorDVS systems. Distinct from most previous work based on heuristics, we aim at the provision of approximated solutions with worst-case guarantees. The proposed algorithms are evaluated by a series of experiments to provide insights in system designs.