The increasing prominence of portable systems and the need to limit power consumption and hence, heat dissipation in very high density VLSI chips have led to rapid and innovative developments in low power design recently. Leakage control is becoming critically important for deep sub-100nm technologies due to the scaling down of threshold voltage and gate oxide thickness of transistors. In this paper, we discuss major sources of power dissipation in VLSI systems, and various low power design techniques on the technology and circuit level, logic level, and system level. Categories and Subject Descriptors B.7.0 [Integrated Circuits]: General. B.7.0 [Integrated Circuits]: Types and design styles. General Terms Design, Performance. Keywords CMOS VLSI, Low Power Integrated Circuits.