MTBE in gasoline is a highly controversial subject. California currently uses about 4 million gallons of MTBE each day - about 10% of our gasoline supply. Governor Davis issued an order to ban MTBE in the future, and other states and the EPA may follow. This talk will discuss some of the issues around the introduction and removal of MTBE from reformulated gasoline. What is MTBE and why is it used in gasoline? What effect does it have on automobile emissions? How much science is involved in this billion-dollar issue?