This tutorial surveys recent advances in asynchronous design methodologies. Whenever possible, actual design examples are used to present the methods. Three primary topics are discussed: (1) asynchronous controllers, (2) asynchronous datapaths, and (3) asynchronous systems. For asynchronous controllers, basic design styles and tools are presented. For asynchronous datapaths, basic issues in timed vs. self-timed, matched delay vs. completion sensing, and power vs. performance tradeoff are discussed. For asynchronous systems, recently fabricated system design examples in processors, co-processors, and DSP's are described.