The 2012 International Technology Roadmap for Semiconductors (ITRS) [1] states that asynchronous circuits currently account for 22% of logic within the multibillion dollar semiconductor industry, and predicts that this percentage will more than double over the next 10 years. Asynchronous logic has been around for the past 50+ years, but, until recently, synchronous circuits have been good enough to meet industry needs, so asynchronous circuits were primarily utilized for niche markets and in the research domain. However, as transistor size continues to decrease, asynchronous circuits are being looked to by industry to solve power dissipation and process variability issues associated with these emerging sub-90 nm circuits. This chapter details the state of the art of asynchronous logic, how asynchronous circuits are currently being utilized in the industry, and the future of asynchronous logic.