Low-power wireless system design requires optimization at all levels of the design abstraction. Sub-1V operation is the key to lowpower design and requires modification of the process technology (e.g., multiple threshold devices, variable threshold devices using bulk biasing or dual-gate SO1 technology, etc.), circuit optimization, and architecture optimization. The CAD tool requirements for these new technologies will be discussed. High-efficiency DC-DC converters are critical for low-voltage and low (and variable) current load operation. Architectural power estimation tools, which accurately model switching activity and interconnect, are the key to fast and efficient exploration of the design space. A systematic approach to low-power design can result in orders of magnitude power reduction.