The inhaled anesthetics were officially introduced to American medicine more than 160 years ago and rank among the most important medical advances in our time. These drugs are used to render patients insensible over twenty million times each year and are the most dangerous of all drugs that physicians currently use. An entire medical specialty, anesthesiology, has arisen out of the need for the special training to administer them safely. Nevertheless, side effects, toxicity, and long-term cognitive problems continue to plague their use, especially in the very sick or aged. Hence, it is essential that we develop an understanding of their molecular pharmacology so that safer alternatives can be developed.