Cocaine and amphetamine are psychoactive agents that increase central nervous system (CNS) activity and produce powerful reinforcing effects (e.g., euphoria, elevated mood, high) that contribute to their high abuse liability. Since the peak of the cocaine epidemic in the mid-1980s, addiction to this stimulant has been a major public health concern. Recently, localized epidemics of amphetamine abuse have developed, particularly in the Western United States. In addition, misuse of prescription stimulants has increased exponentially in the past several years, particularly among adolescents and young adults. The dangers associated with stimulant use are enormous and include increased risk of HIV infection, detrimental effects on the unborn and newborn, and increased crime and violence as well as medical, financial, and psychological problems. Because of these consequences, the task of identifying, characterizing, and developing treatments is more important than ever.