 Tolerance for the sedative effects of alcohol has been shown in young adults to predict development of alcoholism later in life. The basis for this increased risk is unclear. It may be that persons who tolerate alcohol well as young adults experience more of the rewarding effects of alcohol e.g., euphoria, or that they experience less of the negative effects of alcohol e.g., sedation, or some combination of the two. Fortunately, brain-imaging tools can shed light on the brains reward response mechanisms to alcohol. Differences in the reward circuits of persons who experience a euphoric response to alcohol may help explain why some people go on to develop alcoholism while others do not. Both human and animal research point toward a difference in the density of dopamine receptors in the striatum of alcohol-preferring and non alcohol-preferring subjects. The following experiment is designed to examine the relationship between response to alcohol, dopamine receptor density in the striatum, and dopamine release in response to alcohol. 